<s>
The	O
Z80	B-General_Concept
is	O
an	O
8-bit	O
microprocessor	B-Architecture
introduced	O
by	O
Zilog	O
as	O
the	O
startup	O
company	O
's	O
first	O
product	O
.	O
</s>
<s>
The	O
Z80	B-General_Concept
was	O
conceived	O
by	O
Federico	O
Faggin	O
in	O
late	O
1974	O
and	O
developed	O
by	O
him	O
and	O
his	O
11	O
employees	O
starting	O
in	O
early	O
1975	O
.	O
</s>
<s>
With	O
the	O
revenue	O
from	O
the	O
Z80	B-General_Concept
,	O
the	O
company	O
built	O
its	O
own	O
chip	B-Algorithm
factories	I-Algorithm
and	O
grew	O
to	O
over	O
a	O
thousand	O
employees	O
over	O
the	O
following	O
two	O
years	O
.	O
</s>
<s>
The	O
Zilog	B-General_Concept
Z80	I-General_Concept
is	O
a	O
software-compatible	B-General_Concept
extension	O
and	O
enhancement	O
of	O
the	O
Intel	O
8080	B-General_Concept
and	O
,	O
like	O
it	O
,	O
was	O
mainly	O
aimed	O
at	O
embedded	B-Architecture
systems	I-Architecture
.	O
</s>
<s>
Although	O
used	O
in	O
that	O
role	O
,	O
the	O
Z80	B-General_Concept
also	O
became	O
one	O
of	O
the	O
most	O
widely	O
used	O
CPUs	B-General_Concept
in	O
desktop	B-Device
computers	I-Device
and	O
home	O
computers	O
from	O
the	O
1970s	O
to	O
the	O
mid-1980s	O
.	O
</s>
<s>
It	O
was	O
also	O
common	O
in	O
military	O
applications	O
,	O
musical	O
equipment	O
such	O
as	O
synthesizers	O
(	O
like	O
the	O
Roland	O
Jupiter-8	O
)	O
,	O
and	O
coin-operated	O
arcade	O
games	O
of	O
the	O
late	O
1970s	O
and	O
early	O
1980s	O
,	O
including	O
Pac-Man	B-Application
.	O
</s>
<s>
Zilog	O
licensed	O
the	O
Z80	B-General_Concept
to	O
the	O
US-based	O
Synertek	O
and	O
Mostek	O
,	O
which	O
had	O
helped	O
them	O
with	O
initial	O
production	O
,	O
as	O
well	O
as	O
to	O
a	O
European	O
second-source	O
manufacturer	O
SGS	O
.	O
</s>
<s>
The	O
design	B-Architecture
was	O
also	O
copied	O
by	O
several	O
Japanese	O
,	O
East	O
European	O
and	O
Soviet	O
manufacturers	O
.	O
</s>
<s>
This	O
won	O
the	O
Z80	B-General_Concept
acceptance	O
in	O
the	O
world	O
market	O
since	O
large	O
companies	O
like	O
NEC	O
,	O
Toshiba	O
,	O
Sharp	O
,	O
and	O
Hitachi	O
started	O
to	O
manufacture	O
the	O
device	O
(	O
or	O
their	O
own	O
Z80-compatible	O
clones	O
or	O
designs	O
)	O
.	O
</s>
<s>
In	O
recent	O
decades	O
Zilog	O
has	O
refocused	O
on	O
the	O
ever-growing	O
market	O
for	O
embedded	B-Architecture
systems	I-Architecture
,	O
and	O
the	O
most	O
recent	O
Z80-compatible	O
microcontroller	B-Architecture
family	O
,	O
the	O
fully	O
pipelined	B-General_Concept
24-bit	O
eZ80	B-Device
with	O
a	O
linear	B-General_Concept
16MB	O
address	B-General_Concept
range	I-General_Concept
,	O
has	O
been	O
successfully	O
introduced	O
alongside	O
the	O
simpler	O
Z80	B-General_Concept
and	O
Z180	B-Device
products	O
.	O
</s>
<s>
Physicist	O
and	O
engineer	O
Federico	O
Faggin	O
worked	O
at	O
Intel	O
on	O
microprocessor	B-Architecture
design	B-Architecture
.	O
</s>
<s>
At	O
Fairchild	O
Semiconductor	O
,	O
and	O
later	O
at	O
Intel	O
,	O
Faggin	O
had	O
been	O
working	O
on	O
fundamental	O
transistor	B-Application
and	O
semiconductor	O
manufacturing	O
technology	O
.	O
</s>
<s>
He	O
also	O
developed	O
the	O
basic	O
design	B-Architecture
methodology	O
used	O
for	O
memories	O
and	O
microprocessors	B-Architecture
at	O
Intel	O
and	O
led	O
the	O
work	O
on	O
the	O
Intel	B-General_Concept
4004	I-General_Concept
,	O
the	O
Intel	B-General_Concept
8080	I-General_Concept
and	O
several	O
other	O
ICs	O
.	O
</s>
<s>
Masatoshi	O
Shima	O
was	O
the	O
principal	O
logic	O
and	O
transistor-level	O
designer	O
of	O
the	O
4004	B-General_Concept
and	O
the	O
8080	B-General_Concept
under	O
Faggin	O
's	O
supervision	O
,	O
while	O
Ralph	O
Ungermann	O
was	O
in	O
charge	O
of	O
custom	O
integrated	O
circuit	O
design	B-Architecture
.	O
</s>
<s>
In	O
early	O
1974	O
,	O
Intel	O
viewed	O
their	O
microprocessors	B-Architecture
not	O
so	O
much	O
as	O
products	O
to	O
be	O
sold	O
on	O
their	O
own	O
but	O
as	O
a	O
way	O
to	O
sell	O
more	O
of	O
their	O
main	O
products	O
,	O
static	B-Architecture
RAM	I-Architecture
and	O
ROM	B-Device
.	O
</s>
<s>
A	O
reorganization	O
placed	O
many	O
of	O
the	O
formerly	O
independent	O
sections	O
under	O
the	O
direction	O
of	O
Les	O
Vadasz	O
,	O
and	O
a	O
new	O
group	O
was	O
set	O
up	O
to	O
directly	O
market	O
the	O
microprocessors	B-Architecture
.	O
</s>
<s>
When	O
Shima	O
heard	O
,	O
he	O
asked	O
to	O
come	O
to	O
the	O
new	O
company	O
as	O
well	O
,	O
but	O
having	O
no	O
actual	O
product	O
design	B-Architecture
or	O
money	O
,	O
they	O
told	O
him	O
to	O
wait	O
.	O
</s>
<s>
The	O
newly-formed	O
and	O
unnamed	O
company	O
initially	O
began	O
designing	O
a	O
single-chip	O
microcontroller	B-Architecture
called	O
the	O
2001	O
.	O
</s>
<s>
They	O
met	O
with	O
Synertek	O
to	O
discuss	O
fabrication	O
on	O
their	O
lines	O
,	O
and	O
when	O
Faggin	O
began	O
to	O
understand	O
the	O
costs	O
involved	O
it	O
became	O
clear	O
that	O
a	O
low-cost	O
product	O
like	O
this	O
would	O
not	O
be	O
able	O
to	O
compete	O
with	O
a	O
design	B-Architecture
from	O
a	O
company	O
with	O
its	O
own	O
production	O
lines	O
,	O
like	O
Intel	O
.	O
</s>
<s>
They	O
then	O
began	O
considering	O
a	O
more	O
complex	O
microprocessor	B-Architecture
instead	O
,	O
initially	O
known	O
as	O
the	O
Super	O
80	O
,	O
with	O
the	O
main	O
feature	O
being	O
its	O
use	O
of	O
a	O
+5V	O
bus	O
instead	O
of	O
the	O
more	O
common	O
-5	O
,	O
+5	O
and	O
12V	O
used	O
by	O
designs	O
like	O
the	O
8080	B-General_Concept
.	O
</s>
<s>
The	O
new	O
design	B-Architecture
was	O
intended	O
to	O
be	O
compatible	O
with	O
the	O
8080	B-General_Concept
,	O
but	O
add	O
many	O
of	O
the	O
nice	O
features	O
of	O
the	O
Motorola	B-Device
6800	I-Device
,	O
including	O
index	B-General_Concept
registers	I-General_Concept
and	O
improved	O
interrupts	B-Application
.	O
</s>
<s>
This	O
attracted	O
the	O
attention	O
of	O
Exxon	O
Enterprises	O
,	O
Exxon	O
's	O
high-tech	O
investment	O
arm	O
.	O
</s>
<s>
With	O
funding	O
being	O
discussed	O
,	O
and	O
a	O
design	B-Architecture
to	O
be	O
built	O
,	O
Shima	O
joined	O
in	O
February	O
1975	O
.	O
</s>
<s>
Shima	O
immediately	O
set	O
about	O
producing	O
a	O
high-level	O
design	B-Architecture
,	O
adding	O
several	O
concepts	O
of	O
his	O
own	O
.	O
</s>
<s>
In	O
particular	O
,	O
he	O
used	O
his	O
experience	O
on	O
NEC	O
minicomputers	B-Architecture
to	O
add	O
the	O
concept	O
of	O
two	O
sets	O
of	O
processor	B-General_Concept
registers	I-General_Concept
so	O
they	O
could	O
quickly	O
respond	O
to	O
interrupts	B-Application
.	O
</s>
<s>
Ungerman	O
began	O
the	O
development	O
of	O
a	O
series	O
of	O
related	O
controllers	O
and	O
peripheral	O
chips	O
that	O
would	O
complement	O
the	O
design	B-Architecture
.	O
</s>
<s>
Through	O
this	O
period	O
,	O
Shima	O
developed	O
a	O
legendary	O
reputation	O
for	O
being	O
able	O
to	O
convert	O
logic	O
concepts	O
into	O
physical	O
design	B-Architecture
in	O
realtime	O
;	O
while	O
discussing	O
a	O
proposed	O
feature	O
,	O
he	O
would	O
often	O
interrupt	B-Application
and	O
state	O
how	O
much	O
room	O
that	O
would	O
take	O
on	O
the	O
chip	O
and	O
veto	O
its	O
addition	O
if	O
it	O
was	O
too	O
large	O
.	O
</s>
<s>
The	O
first	O
pass	O
at	O
the	O
design	B-Architecture
was	O
complete	O
by	O
April	O
1975	O
.	O
</s>
<s>
A	O
second	O
version	O
of	O
the	O
logic	O
design	B-Architecture
was	O
issued	O
on	O
7	O
August	O
and	O
the	O
bus	O
details	O
by	O
16	O
September	O
.	O
</s>
<s>
By	O
this	O
time	O
,	O
Synertek	O
and	O
Mostek	O
had	O
both	O
set	O
up	O
the	O
depletion-mode	O
production	O
lines	O
that	O
could	O
be	O
used	O
to	O
produce	O
the	O
design	B-Architecture
.	O
</s>
<s>
However	O
,	O
the	O
president	O
of	O
Synertek	O
demanded	O
that	O
the	O
company	O
be	O
given	O
a	O
second	O
source	O
license	O
,	O
allowing	O
them	O
to	O
sell	O
the	O
design	B-Architecture
directly	O
.	O
</s>
<s>
By	O
the	O
end	O
of	O
the	O
month	O
,	O
they	O
had	O
also	O
completed	O
a	O
assembler-based	O
development	O
system	O
.	O
</s>
<s>
Some	O
of	O
the	O
Z80	B-General_Concept
support	O
and	O
peripheral	O
ICs	O
were	O
under	O
development	O
at	O
this	O
point	O
,	O
and	O
many	O
of	O
them	O
were	O
launched	O
during	O
the	O
following	O
year	O
.	O
</s>
<s>
Among	O
them	O
were	O
the	O
Z80	B-General_Concept
CTC	O
(	O
counter/timer	O
)	O
,	O
Z80	B-General_Concept
DMA	O
(	O
direct	O
memory	O
access	O
)	O
,	O
Z80	B-General_Concept
DART	O
(	O
dual	O
asynchronous	O
receiver	O
–	O
transmitter	O
)	O
,	O
Z80	B-General_Concept
SIO	O
(	O
synchronous	O
communication	O
controller	O
)	O
,	O
and	O
Z80	B-General_Concept
PIO	O
(	O
parallel	O
input/output	B-General_Concept
)	O
.	O
</s>
<s>
The	O
Z80	B-General_Concept
was	O
officially	O
launched	O
in	O
July	O
1976	O
.	O
</s>
<s>
The	O
Zilog	O
team	O
had	O
worried	O
about	O
this	O
,	O
and	O
Faggin	O
had	O
come	O
up	O
with	O
the	O
idea	O
of	O
adding	O
transistors	B-Application
that	O
would	O
be	O
subtly	O
modified	O
to	O
operate	O
differently	O
than	O
a	O
visual	O
inspection	O
would	O
suggest	O
.	O
</s>
<s>
Shima	O
added	O
six	O
of	O
these	O
"	O
traps	B-Application
"	O
around	O
the	O
design	B-Architecture
.	O
</s>
<s>
Sometime	O
later	O
,	O
Shima	O
was	O
told	O
by	O
an	O
engineer	O
within	O
NEC	O
that	O
the	O
traps	B-Application
had	O
delayed	O
their	O
copying	O
efforts	O
by	O
six	O
months	O
.	O
</s>
<s>
The	O
successful	O
launch	O
allowed	O
Faggin	O
and	O
Ungermann	O
to	O
approach	O
Exxon	O
looking	O
for	O
funding	O
to	O
build	O
their	O
own	O
fab	B-Algorithm
.	O
</s>
<s>
This	O
allowed	O
them	O
to	O
capture	O
about	O
60	O
to	O
70%	O
of	O
the	O
total	O
market	O
for	O
Z80	B-General_Concept
sales	O
.	O
</s>
<s>
Faggin	O
designed	O
the	O
instruction	B-General_Concept
set	I-General_Concept
to	O
be	O
binary	B-General_Concept
compatible	I-General_Concept
with	O
the	O
8080	B-General_Concept
so	O
that	O
most	O
8080	B-General_Concept
code	O
,	O
notably	O
the	O
CP/M	B-Application
operating	I-Application
system	I-Application
and	O
Intel	O
's	O
PL/M	B-Language
compiler	O
for	O
8080	B-General_Concept
(	O
as	O
well	O
as	O
its	O
generated	O
code	O
)	O
,	O
would	O
run	O
unmodified	O
on	O
the	O
new	O
Z80	B-General_Concept
CPU	O
.	O
</s>
<s>
Masatoshi	O
Shima	O
designed	O
most	O
of	O
the	O
microarchitecture	B-General_Concept
as	O
well	O
as	O
the	O
gate	O
and	O
transistor	B-Application
levels	O
of	O
the	O
Z80	B-General_Concept
CPU	O
,	O
assisted	O
by	O
a	O
small	O
number	O
of	O
engineers	O
and	O
layout	O
people	O
.	O
</s>
<s>
The	O
Z80	B-General_Concept
offered	O
many	O
improvements	O
over	O
the	O
8080	B-General_Concept
:	O
</s>
<s>
An	O
enhanced	O
instruction	B-General_Concept
set	I-General_Concept
including	O
:	O
</s>
<s>
block	O
copy	O
,	O
block	O
input/output	B-General_Concept
(	O
I/O	B-General_Concept
)	O
,	O
and	O
byte	O
search	O
instructions	O
.	O
</s>
<s>
An	O
overflow	B-Algorithm
flag	I-Algorithm
with	O
better	O
support	O
for	O
signed	O
8	O
-	O
and	O
16-bit	O
arithmetics	O
.	O
</s>
<s>
A	O
better	O
interrupt	B-Application
system	O
:	O
</s>
<s>
A	O
more	O
automatic	O
and	O
general	O
vectorized	B-General_Concept
interrupt	I-General_Concept
system	I-General_Concept
,	O
mode	O
2	O
,	O
primarily	O
intended	O
for	O
Zilog	O
's	O
line	O
of	O
counter/timers	O
,	O
DMA	O
and	O
communications	O
controllers	O
,	O
as	O
well	O
as	O
a	O
fixed	O
vector	O
interrupt	B-Application
system	O
,	O
mode	O
1	O
,	O
for	O
simple	O
systems	O
with	O
minimal	O
hardware	O
(	O
with	O
mode	O
0	O
being	O
the	O
8080-compatible	O
mode	O
)	O
.	O
</s>
<s>
A	O
non-maskable	O
interrupt	B-Application
(	O
NMI	O
)	O
,	O
which	O
can	O
be	O
used	O
to	O
respond	O
to	O
power-down	O
situations	O
or	O
other	O
high-priority	O
events	O
(	O
and	O
allowing	O
a	O
minimalistic	O
Z80	B-General_Concept
system	O
to	O
easily	O
implement	O
a	O
two-level	O
interrupt	B-Application
scheme	O
in	O
mode	O
1	O
)	O
.	O
</s>
<s>
A	O
complete	O
duplicate	O
register	B-General_Concept
file	I-General_Concept
,	O
which	O
could	O
be	O
quickly	O
switched	O
,	O
to	O
speed	O
up	O
response	O
to	O
interrupts	B-Application
such	O
as	O
fast	O
asynchronous	O
event	O
handlers	O
or	O
a	O
multitasking	B-Operating_System
dispatcher	O
.	O
</s>
<s>
Single	O
5-volt	O
power	O
supply	O
(	O
the	O
8080	B-General_Concept
needed	O
−5V	O
,	O
+5V	O
,	O
and	O
+12V	O
)	O
.	O
</s>
<s>
Single-phase	O
5-volt	O
clock	O
(	O
the	O
8080	B-General_Concept
needed	O
a	O
high-amplitude	O
(	O
9	O
to	O
12volts	O
)	O
non-overlapping	O
two-phase	O
clock	O
)	O
.	O
</s>
<s>
Built-in	O
DRAM	B-General_Concept
refresh	I-General_Concept
,	O
which	O
would	O
otherwise	O
require	O
external	O
circuitry	O
,	O
unless	O
SRAM	B-Architecture
,	O
more	O
expensive	O
and	O
less	O
dense	O
(	O
but	O
faster	O
)	O
,	O
was	O
used	O
.	O
</s>
<s>
Non-multiplexed	O
buses	O
(	O
the	O
8080	B-General_Concept
had	O
state	O
signals	O
multiplexed	O
onto	O
the	O
data	O
bus	O
)	O
.	O
</s>
<s>
A	O
special-reset	O
function	O
that	O
clears	O
only	O
the	O
program	O
counter	O
,	O
so	O
that	O
a	O
single	O
Z80	B-General_Concept
CPU	O
could	O
be	O
used	O
in	O
a	O
development	O
system	O
such	O
as	O
an	O
in-circuit	B-Application
emulator	I-Application
.	O
</s>
<s>
The	O
Z80	B-General_Concept
took	O
over	O
from	O
the	O
8080	B-General_Concept
and	O
its	O
offspring	O
,	O
the	O
8085	B-General_Concept
,	O
in	O
the	O
processor	O
market	O
and	O
became	O
one	O
of	O
the	O
most	O
popular	O
and	O
widely	O
used	O
8-bit	O
CPUs	B-General_Concept
.	O
</s>
<s>
Some	O
organizations	O
such	O
as	O
British	O
Telecom	O
remained	O
loyal	O
to	O
the	O
8085	B-General_Concept
for	O
embedded	O
applications	O
,	O
owing	O
to	O
their	O
familiarity	O
with	O
it	O
and	O
to	O
its	O
on-chip	O
serial	O
interface	O
and	O
interrupt	B-Application
architecture	O
.	O
</s>
<s>
Likewise	O
,	O
Zenith	O
Data	O
Systems	O
paired	O
the	O
8085	B-General_Concept
with	O
the	O
16-bit	O
Intel	O
8088	B-Device
in	O
its	O
first	O
MS-DOS	O
computer	O
,	O
the	O
Zenith	B-Device
Z-100	I-Device
,	O
despite	O
having	O
previous	O
experience	O
with	O
its	O
pioneering	O
Z80-based	O
Heathkit	O
H89	O
and	O
Zenith	O
Z-89	O
products	O
.	O
</s>
<s>
However	O
,	O
other	O
computers	O
were	O
made	O
integrating	O
the	O
Z80	B-General_Concept
with	O
other	O
CPUs	B-General_Concept
:	O
the	O
Radio	B-Device
Shack	I-Device
TRS-80	I-Device
Model	O
16	O
with	O
a	O
Motorola	B-Device
68000	I-Device
,	O
the	O
DEC	B-Device
Rainbow	I-Device
with	O
an	O
8088	B-Device
,	O
and	O
the	O
Commodore	O
128	O
with	O
a	O
MOS	O
8502	O
.	O
</s>
<s>
Zilog	O
was	O
later	O
producing	O
a	O
low-power	O
Z80	B-General_Concept
suitable	O
for	O
the	O
growing	O
laptop	B-Device
computer	I-Device
market	O
of	O
the	O
early	O
1980s	O
.	O
</s>
<s>
Intel	O
produced	O
a	O
CMOS	B-Device
8085	B-General_Concept
(	O
80C85	B-General_Concept
)	O
used	O
in	O
battery-powered	O
portable	O
computers	O
,	O
such	O
as	O
the	O
Kyocera-designed	O
laptop	B-Device
from	O
April	O
1983	O
,	O
also	O
sold	O
by	O
Tandy	O
(	O
as	O
TRS-80	B-Device
Model	O
100	O
)	O
,	O
Olivetti	O
,	O
and	O
NEC	O
.	O
</s>
<s>
In	O
following	O
years	O
,	O
however	O
,	O
CMOS	B-Device
versions	O
of	O
the	O
Z80	B-General_Concept
(	O
from	O
both	O
Zilog	O
and	O
Japanese	O
manufacturers	O
)	O
would	O
dominate	O
this	O
market	O
as	O
well	O
,	O
in	O
products	O
such	O
as	O
the	O
Amstrad	B-Device
NC100	I-Device
,	O
Cambridge	O
Z88	O
and	O
Tandy	O
's	O
own	O
WP-2	O
.	O
</s>
<s>
Perhaps	O
a	O
key	O
to	O
the	O
initial	O
success	O
of	O
the	O
Z80	B-General_Concept
was	O
the	O
built-in	O
DRAM	B-General_Concept
refresh	I-General_Concept
,	O
at	O
least	O
in	O
markets	O
such	O
as	O
CP/M	B-Application
and	O
other	O
office	O
and	O
home	O
computers	O
.	O
</s>
<s>
(	O
Most	O
Z80	B-General_Concept
embedded	B-Architecture
systems	I-Architecture
use	O
static	B-Architecture
RAM	I-Architecture
that	O
do	O
not	O
need	O
refresh	B-General_Concept
.	O
)	O
</s>
<s>
It	O
may	O
also	O
have	O
been	O
its	O
minimalistic	O
two-level	O
interrupt	B-Application
system	O
,	O
or	O
conversely	O
,	O
its	O
general	O
multi-level	O
daisy-chain	O
interrupt	B-Application
system	O
useful	O
in	O
servicing	O
multiple	O
Z80	B-General_Concept
IO	O
chips	O
.	O
</s>
<s>
However	O
,	O
others	O
claim	O
that	O
its	O
popularity	O
was	O
due	O
to	O
the	O
duplicated	O
registers	O
that	O
allowed	O
fast	O
context	O
switches	O
or	O
more	O
efficient	O
processing	O
of	O
things	O
like	O
floating-point	B-Algorithm
math	I-Algorithm
compared	O
to	O
8-bit	O
CPUs	B-General_Concept
with	O
fewer	O
registers	O
.	O
</s>
<s>
(	O
The	O
Z80	B-General_Concept
can	O
keep	O
several	O
such	O
numbers	O
internally	O
,	O
using	O
HL'HL	O
,	O
DE'DE	O
and	O
BC'BC	O
as	O
32-bits	O
registers	O
,	O
avoiding	O
having	O
to	O
access	O
them	O
from	O
slower	O
RAM	O
during	O
computation	O
.	O
)	O
</s>
<s>
For	O
the	O
original	O
NMOS	B-Algorithm
design	B-Architecture
,	O
the	O
specified	O
upper	O
clock-frequency	O
limit	O
increased	O
successively	O
from	O
the	O
introductory	O
2.5MHz	O
,	O
via	O
the	O
well	O
known	O
4MHz	O
(	O
Z80A	B-General_Concept
)	O
,	O
up	O
to	O
6	O
(	O
Z80B	B-General_Concept
)	O
and	O
8MHz	O
(	O
Z80H	B-General_Concept
)	O
.	O
</s>
<s>
The	O
NMOS	B-Algorithm
version	O
has	O
been	O
produced	O
as	O
a	O
10MHz	O
part	O
since	O
the	O
late	O
1980s	O
.	O
</s>
<s>
CMOS	B-Device
versions	O
were	O
developed	O
with	O
specified	O
upper	O
frequency	O
limits	O
ranging	O
from	O
4MHz	O
up	O
to	O
20MHz	O
for	O
the	O
version	O
sold	O
today	O
.	O
</s>
<s>
The	O
CMOS	B-Device
versions	O
allowed	O
low-power	O
standby	O
with	O
internal	O
state	O
retained	O
,	O
having	O
no	O
lower	O
frequency	O
limit	O
.	O
</s>
<s>
The	O
fully	O
compatible	O
derivatives	O
HD64180/Z180	O
and	O
eZ80	B-Device
are	O
currently	O
specified	O
for	O
up	O
to	O
33	O
and	O
50MHz	O
respectively	O
.	O
</s>
<s>
The	O
programming	O
model	O
and	O
register	O
set	O
of	O
the	O
Z80	B-General_Concept
are	O
fairly	O
conventional	O
,	O
ultimately	O
based	O
on	O
the	O
register	O
structure	O
of	O
the	O
Datapoint	B-Device
2200	I-Device
.	O
</s>
<s>
The	O
Z80	B-General_Concept
was	O
designed	O
as	O
an	O
extension	O
of	O
the	O
Intel	B-General_Concept
8080	I-General_Concept
,	O
created	O
by	O
the	O
same	O
engineers	O
,	O
which	O
in	O
turn	O
was	O
an	O
extension	O
of	O
the	O
8008	B-General_Concept
.	O
</s>
<s>
The	O
8008	B-General_Concept
was	O
basically	O
a	O
PMOS	B-Algorithm
implementation	O
of	O
the	O
TTL-based	O
CPU	O
of	O
the	O
Datapoint	B-Device
2200	I-Device
.	O
</s>
<s>
The	O
2200	O
design	B-Architecture
allowed	O
8-bit	O
registers	O
H	B-Application
and	O
L	O
(	O
High	O
and	O
Low	O
)	O
to	O
be	O
paired	O
into	O
a	O
16-bit	O
address	B-General_Concept
register	I-General_Concept
HL	O
.	O
</s>
<s>
In	O
the	O
8080	B-General_Concept
,	O
this	O
pairing	O
was	O
added	O
to	O
the	O
BC	O
and	O
DE	O
pairs	O
as	O
well	O
,	O
while	O
HL	O
was	O
generalized	O
to	O
allow	O
use	O
as	O
a	O
16-bit	O
accumulator	B-General_Concept
,	O
not	O
just	O
an	O
address	B-General_Concept
register	I-General_Concept
.	O
</s>
<s>
The	O
8080	B-General_Concept
also	O
introduced	O
the	O
important	O
8-bit	O
immediate	O
data	O
mode	O
for	O
accumulator	B-General_Concept
operations	O
,	O
and	O
immediate	O
16-bit	O
data	O
for	O
HL	O
,	O
BC	O
and	O
DE	O
loads	O
.	O
</s>
<s>
Furthermore	O
,	O
direct	O
16-bit	O
copying	O
between	O
HL	O
and	O
memory	O
was	O
now	O
possible	O
,	O
using	O
a	O
direct	B-Language
address	I-Language
.	O
</s>
<s>
The	O
Z80	B-General_Concept
orthogonalized	B-General_Concept
this	O
further	O
by	O
making	O
all	O
16-bit	O
register	O
pairs	O
,	O
including	O
IX	O
and	O
IY	O
,	O
more	O
general	O
purpose	O
,	O
as	O
well	O
as	O
allowing	O
16-bit	O
copying	O
directly	O
to	O
and	O
from	O
memory	O
for	O
all	O
of	O
these	O
pairs	O
.	O
</s>
<s>
The	O
16-bit	O
IX	O
and	O
IY	O
registers	O
in	O
the	O
Z80	B-General_Concept
are	O
primarily	O
intended	O
as	O
base	O
address-registers	O
,	O
where	O
a	O
particular	O
instruction	O
supplies	O
a	O
constant	O
offset	B-General_Concept
that	O
is	O
added	O
to	O
the	O
previous	O
values	O
,	O
but	O
they	O
are	O
also	O
usable	O
as	O
16-bit	O
accumulators	B-General_Concept
,	O
among	O
other	O
things	O
.	O
</s>
<s>
A	O
limitation	O
is	O
that	O
all	O
operand	O
references	O
involving	O
IX	O
or	O
IY	O
require	O
an	O
extra	O
instruction	O
prefix	O
byte	O
,	O
adding	O
at	O
least	O
four	O
clock	O
cycles	O
over	O
the	O
timing	O
of	O
an	O
instruction	O
using	O
HL	O
instead	O
;	O
this	O
sometimes	O
makes	O
using	O
IX	O
or	O
IY	O
less	O
efficient	O
than	O
a	O
method	O
using	O
only	O
the	O
8080-model	O
registers	O
.	O
</s>
<s>
The	O
Z80	B-General_Concept
also	O
introduced	O
a	O
new	O
signed	O
overflow	B-Algorithm
flag	I-Algorithm
and	O
complemented	O
the	O
fairly	O
simple	O
16-bit	O
arithmetics	O
of	O
the	O
8080	B-General_Concept
with	O
dedicated	O
instructions	O
for	O
signed	O
16-bit	O
arithmetics	O
.	O
</s>
<s>
The	O
8080-compatible	O
registers	O
AF	O
,	O
BC	O
,	O
DE	O
,	O
HL	O
are	O
duplicated	O
as	O
a	O
separate	O
register	B-General_Concept
file	I-General_Concept
in	O
the	O
Z80	B-General_Concept
,	O
where	O
the	O
processor	O
can	O
quickly	O
(	O
four	O
t-states	O
,	O
the	O
least	O
possible	O
execution	O
time	O
for	O
any	O
Z80	B-General_Concept
instruction	O
)	O
switch	O
from	O
one	O
bank	O
to	O
the	O
other	O
;	O
a	O
feature	O
useful	O
for	O
speeding	O
up	O
responses	O
to	O
single-level	O
,	O
high-priority	O
interrupts	B-Application
.	O
</s>
<s>
The	O
dual	O
register-set	O
is	O
very	O
useful	O
in	O
the	O
embedded	O
role	O
,	O
as	O
it	O
improves	O
interrupt	B-Application
handling	I-Application
performance	O
,	O
but	O
found	O
widespread	O
use	O
in	O
the	O
personal	O
computer	O
role	O
as	O
an	O
additional	O
set	O
of	O
general	O
registers	O
for	O
complex	O
code	O
like	O
floating-point	B-Algorithm
arithmetic	I-Algorithm
or	O
home	O
computer	O
games	O
.	O
</s>
<s>
The	O
duplicate	O
register	B-General_Concept
file	I-General_Concept
is	O
often	O
referred	O
to	O
as	O
the	O
"	O
alternate	O
register	O
set	O
"	O
(	O
by	O
some	O
,	O
the	O
"	O
primed	O
"	O
register	B-General_Concept
file	I-General_Concept
since	O
the	O
apostrophe	O
character	O
is	O
used	O
to	O
denote	O
them	O
in	O
assembler	B-Language
source	O
code	O
and	O
the	O
Zilog	O
documentation	O
)	O
.	O
</s>
<s>
However	O
,	O
the	O
8-bit	O
accumulator	B-General_Concept
A	O
with	O
its	O
flag	O
register	O
F	O
is	O
bifurcated	O
from	O
the	O
"	O
general	O
purpose	O
"	O
register	O
pairs	O
HL	O
,	O
DE	O
and	O
BC	O
.	O
</s>
<s>
Thus	O
the	O
accumulator	B-General_Concept
A	O
can	O
interact	O
independently	O
with	O
any	O
of	O
the	O
general	O
purpose	O
8-bit	O
registers	O
in	O
the	O
alternate	O
(	O
or	O
primed	O
)	O
register	B-General_Concept
file	I-General_Concept
,	O
or	O
,	O
if	O
HL	O
 '	O
contains	O
a	O
pointer	O
to	O
memory	O
,	O
some	O
byte	O
there	O
(	O
DE	O
 '	O
and	O
BC	O
 '	O
can	O
also	O
transfer	O
8-bit	O
data	O
between	O
memory	O
and	O
accumulator	B-General_Concept
A	O
)	O
.	O
</s>
<s>
The	O
only	O
way	O
for	O
the	O
programmer	O
to	O
tell	O
which	O
set(s )	O
are	O
in	O
context	O
(	O
while	O
"	O
playing	O
computer	O
"	O
while	O
scrutinizing	O
the	O
assembler	B-Language
source	O
text	O
,	O
or	O
worse	O
,	O
poring	O
over	O
code	O
with	O
a	O
debugger	O
)	O
is	O
to	O
trace	O
where	O
each	O
register	O
swap	O
is	O
made	O
at	O
each	O
point	O
in	O
the	O
program	O
.	O
</s>
<s>
Obviously	O
if	O
many	O
jump	O
and	O
calls	O
are	O
made	O
within	O
these	O
code	O
segments	O
it	O
can	O
quickly	O
become	O
difficult	O
to	O
tell	O
which	O
register	B-General_Concept
file	I-General_Concept
is	O
in	O
context	O
unless	O
carefully	O
commented	O
.	O
</s>
<s>
The	O
Zilog	B-Device
Z280	I-Device
instruction	B-General_Concept
set	I-General_Concept
includes	O
JAF	O
and	O
JAR	O
instructions	O
which	O
jump	O
to	O
a	O
destination	O
address	O
if	O
the	O
alternate	O
registers	O
are	O
in	O
context	O
(	O
thus	O
officially	O
recognizing	O
this	O
programming	O
complication	O
)	O
.	O
</s>
<s>
As	O
on	O
the	O
8080	B-General_Concept
,	O
8-bit	O
registers	O
are	O
typically	O
paired	O
to	O
provide	O
16-bit	O
versions	O
.	O
</s>
<s>
The	O
8080	B-General_Concept
compatible	O
registers	O
are	O
:	O
</s>
<s>
The	O
new	O
registers	O
introduced	O
with	O
the	O
Z80	B-General_Concept
are	O
:	O
</s>
<s>
The	O
refresh	B-General_Concept
register	O
,	O
R	O
,	O
increments	O
each	O
time	O
the	O
CPU	O
fetches	O
an	O
opcode	O
(	O
or	O
an	O
opcode	O
prefix	O
,	O
which	O
internally	O
executes	O
like	O
a	O
1-byte	O
instruction	O
)	O
and	O
has	O
no	O
simple	O
relationship	O
with	O
program	O
execution	O
.	O
</s>
<s>
This	O
has	O
sometimes	O
been	O
used	O
to	O
generate	O
pseudorandom	B-Error_Name
numbers	I-Error_Name
in	O
games	O
,	O
and	O
also	O
in	O
software	O
protection	O
schemes	O
.	O
</s>
<s>
It	O
has	O
also	O
been	O
employed	O
as	O
a	O
"	O
hardware	O
"	O
counter	O
in	O
some	O
designs	O
;	O
an	O
example	O
of	O
this	O
is	O
the	O
ZX81	O
,	O
which	O
lets	O
it	O
keep	O
track	O
of	O
character	O
positions	O
on	O
the	O
TV	O
screen	O
by	O
triggering	O
an	O
interrupt	B-Application
at	O
wrap	B-Error_Name
around	I-Error_Name
(	O
by	O
connecting	O
INT	O
to	O
A6	O
)	O
.	O
</s>
<s>
The	O
interrupt	B-General_Concept
vector	I-General_Concept
register	O
,	O
I	O
,	O
is	O
used	O
for	O
the	O
Z80	B-General_Concept
specific	O
mode	O
2	O
interrupts	B-Application
(	O
selected	O
by	O
the	O
IM	O
2	O
instruction	O
)	O
.	O
</s>
<s>
It	O
supplies	O
the	O
high	O
byte	O
of	O
the	O
base	O
address	O
for	O
a	O
128-entry	O
table	O
of	O
service	B-General_Concept
routine	I-General_Concept
addresses	O
which	O
are	O
selected	O
via	O
an	O
index	O
sent	O
to	O
the	O
CPU	O
during	O
an	O
interrupt	B-Application
acknowledge	O
cycle	O
;	O
this	O
index	O
is	O
simply	O
the	O
low	O
byte	O
part	O
of	O
the	O
pointer	O
to	O
the	O
tabulated	O
indirect	B-Language
address	I-Language
pointing	O
to	O
the	O
service	B-General_Concept
routine	I-General_Concept
.	O
</s>
<s>
The	O
pointer	O
identifies	O
a	O
particular	O
peripheral	O
chip	O
or	O
peripheral	O
function	O
or	O
event	O
,	O
where	O
the	O
chips	O
are	O
normally	O
connected	O
in	O
a	O
so-called	O
daisy	B-Application
chain	I-Application
for	O
priority	O
resolution	O
.	O
</s>
<s>
Like	O
the	O
refresh	B-General_Concept
register	O
,	O
this	O
register	O
has	O
also	O
sometimes	O
been	O
used	O
creatively	O
;	O
in	O
interrupt	B-Application
modes	O
0	O
and	O
1	O
(	O
or	O
in	O
a	O
system	O
not	O
using	O
interrupts	B-Application
)	O
it	O
can	O
be	O
used	O
as	O
simply	O
another	O
8-bit	O
data	O
register	O
.	O
</s>
<s>
The	O
instructions	O
LD	O
A	O
,	O
R	O
and	O
LD	O
A	O
,	O
I	O
affect	O
the	O
Z80	B-General_Concept
flags	O
register	O
,	O
unlike	O
all	O
the	O
other	O
LD	O
(	O
load	O
)	O
instructions	O
.	O
</s>
<s>
The	O
Sign	O
(	O
bit	O
7	O
)	O
and	O
Zero	O
(	O
bit	O
6	O
)	O
flags	O
are	O
set	O
according	O
to	O
the	O
data	O
loaded	O
from	O
the	O
Refresh	B-General_Concept
or	O
Interrupt	B-Application
source	O
registers	O
.	O
</s>
<s>
Although	O
the	O
Z80	B-General_Concept
is	O
generally	O
considered	O
an	O
eight-bit	O
CPU	O
,	O
it	O
has	O
a	O
four-bit	O
ALU	B-General_Concept
,	O
so	O
calculations	O
are	O
done	O
in	O
two	O
cycles	O
.	O
</s>
<s>
The	O
first	O
Intel	B-General_Concept
8008	I-General_Concept
assembly	B-Language
language	I-Language
was	O
based	O
on	O
a	O
very	O
simple	O
(	O
but	O
systematic	O
)	O
syntax	O
inherited	O
from	O
the	O
Datapoint	B-Device
2200	I-Device
design	B-Architecture
.	O
</s>
<s>
This	O
original	O
syntax	O
was	O
later	O
transformed	O
into	O
a	O
new	O
,	O
somewhat	O
more	O
traditional	O
,	O
assembly	B-Language
language	I-Language
form	O
for	O
this	O
same	O
original	O
8008	B-General_Concept
chip	O
.	O
</s>
<s>
At	O
about	O
the	O
same	O
time	O
,	O
the	O
new	O
assembly	B-Language
language	I-Language
was	O
also	O
extended	O
to	O
accommodate	O
the	O
additional	O
addressing	B-Language
modes	I-Language
in	O
the	O
more	O
advanced	O
Intel	B-General_Concept
8080	I-General_Concept
chip	O
(	O
the	O
8008	B-General_Concept
and	O
8080	B-General_Concept
shared	O
a	O
language	O
subset	O
without	O
being	O
binary	B-General_Concept
compatible	I-General_Concept
;	O
however	O
,	O
the	O
8008	B-General_Concept
was	O
binary	B-General_Concept
compatible	I-General_Concept
with	O
the	O
Datapoint	B-Device
2200	I-Device
)	O
.	O
</s>
<s>
The	O
mnemonic	O
letter	O
M	O
,	O
for	O
memory	O
(	O
referenced	O
by	O
HL	O
)	O
,	O
was	O
lifted	O
out	O
from	O
within	O
the	O
instruction	O
mnemonic	O
to	O
become	O
a	O
syntactically	O
freestanding	O
operand	O
,	O
while	O
registers	O
and	O
combinations	O
of	O
registers	O
became	O
very	O
inconsistently	O
denoted	O
;	O
either	O
by	O
abbreviated	O
operands	O
(	O
MVI	O
D	O
,	O
LXI	O
H	B-Application
and	O
so	O
on	O
)	O
,	O
within	O
the	O
instruction	O
mnemonic	O
itself	O
(	O
LDA	O
,	O
LHLD	O
and	O
so	O
on	O
)	O
,	O
or	O
both	O
at	O
the	O
same	O
time	O
(	O
LDAX	O
B	O
,	O
STAX	O
D	O
and	O
so	O
on	O
)	O
.	O
</s>
<s>
Intel	O
8008Datapoint	O
2200	O
Intel	O
8080Intel	O
8085	B-General_Concept
Zilog	O
Z80	B-General_Concept
Intel	O
8086/Intel	O
8088	B-Device
before	O
ca	O
.	O
</s>
<s>
1974	O
1976	O
1978	O
LBC	O
MOV	O
B	O
,	O
C	B-Algorithm
LD	O
B	O
,	O
C	B-Algorithm
MOV	O
CH	O
,	O
CL	O
--	O
LDAX	O
B	O
LD	O
A	O
,	O
(	O
BC	O
)	O
--	O
LAM	O
MOV	O
A	O
,	O
M	O
LD	O
A	O
,	O
(	O
HL	O
)	O
MOV	O
AL,[BX]	O
LBM	O
MOV	O
B	O
,	O
M	O
LD	O
B	O
,	O
(	O
HL	O
)	O
MOV	O
CH,[BX]	O
--	O
STAX	O
D	O
LD	O
(	O
DE	O
)	O
,	O
A	O
--	O
LMA	O
MOV	O
M	O
,	O
A	O
LD	O
(	O
HL	O
)	O
,	O
A	O
MOV	O
[BX],AL	O
LMC	O
MOV	O
M	O
,	O
C	B-Algorithm
LD	O
(	O
HL	O
)	O
,	O
C	B-Algorithm
MOV	O
[BX],CL	O
LDI	O
56	O
MVI	O
D	O
,	O
56	O
LD	O
D	O
,	O
56	O
MOV	O
DL	O
,	O
56	O
LMI	O
56	O
MVI	O
M	O
,	O
56	O
LD	O
(	O
HL	O
)	O
,	O
56	O
MOV	O
byte	O
ptr	O
[BX],56	O
--	O
LDA	O
1234	O
LD	O
A	O
,	O
(	O
1234	O
)	O
MOV	O
AL,[1234]	O
--	O
STA	O
1234	O
LD	O
(	O
1234	O
)	O
,	O
A	O
MOV	O
[1234],AL	O
--	O
--	O
LD	O
B	O
,	O
(	O
IX+56	O
)	O
MOV	O
CH,[SI+56]	O
--	O
--	O
LD	O
(	O
IX+56	O
)	O
,	O
C	B-Algorithm
MOV	O
[SI+56],CL	O
--	O
--	O
LD	O
(	O
IY+56	O
)	O
,	O
78	O
MOV	O
byte	O
ptr	O
[DI+56],78	O
--	O
LXI	O
B	O
,	O
1234	O
LD	O
BC	O
,	O
1234	O
MOV	O
CX	O
,	O
1234	O
--	O
LXI	O
H	B-Application
,	O
1234	O
LD	O
HL	O
,	O
1234	O
MOV	O
BX	O
,	O
1234	O
--	O
SHLD	O
1234	O
LD	O
(	O
1234	O
)	O
,	O
HL	O
MOV	O
[1234],BX	O
--	O
LHLD	O
1234	O
LD	O
HL	O
,	O
(	O
1234	O
)	O
MOV	O
BX,[1234]	O
--	O
--	O
LD	O
BC	O
,	O
(	O
1234	O
)	O
MOV	O
CX,[1234]	O
--	O
--	O
LD	O
IX	O
,	O
(	O
1234	O
)	O
MOV	O
SI,[1234]Illustration	O
of	O
four	O
syntaxes	O
,	O
using	O
samples	O
of	O
equivalent	O
,	O
or	O
(	O
for	O
8086	B-General_Concept
)	O
very	O
similar	O
,	O
load	B-General_Concept
and	I-General_Concept
store	I-General_Concept
instructions	I-General_Concept
.	O
</s>
<s>
The	O
Z80	B-General_Concept
syntax	O
uses	O
parentheses	O
around	O
an	O
expression	O
to	O
indicate	O
that	O
the	O
value	O
should	O
be	O
used	O
as	O
a	O
memory	O
address	O
(	O
as	O
mentioned	O
below	O
)	O
,	O
while	O
the	O
8086	B-General_Concept
syntax	O
uses	O
brackets	O
instead	O
of	O
ordinary	O
parentheses	O
for	O
this	O
purpose	O
.	O
</s>
<s>
Both	O
Z80	B-General_Concept
and	O
8086	B-General_Concept
use	O
the	O
+	O
sign	O
to	O
indicate	O
that	O
a	O
constant	O
is	O
added	O
to	O
a	O
base	O
register	O
to	O
form	O
an	O
address	O
.	O
</s>
<s>
Note	O
that	O
the	O
8086	B-General_Concept
is	O
not	O
a	O
complete	O
superset	O
of	O
the	O
Z80	B-General_Concept
.	O
</s>
<s>
BX	O
is	O
the	O
only	O
8086	B-General_Concept
register	O
pair	O
that	O
can	O
be	O
used	O
as	O
a	O
pointer	O
.	O
</s>
<s>
Because	O
Intel	O
claimed	O
a	O
copyright	O
on	O
their	O
assembly	O
mnemonics	O
,	O
a	O
new	O
assembly	O
syntax	O
had	O
to	O
be	O
developed	O
for	O
the	O
Z80	B-General_Concept
.	O
</s>
<s>
All	O
load	B-General_Concept
and	I-General_Concept
store	I-General_Concept
instructions	I-General_Concept
use	O
the	O
same	O
mnemonic	O
name	O
,	O
LD	O
,	O
for	O
LOAD	O
(	O
a	O
return	O
to	O
the	O
simplistic	O
Datapoint	B-Device
2200	I-Device
vocabulary	O
)	O
;	O
other	O
common	O
instructions	O
,	O
such	O
as	O
ADD	O
and	O
INC	O
,	O
use	O
the	O
same	O
mnemonic	O
regardless	O
of	O
addressing	B-Language
mode	I-Language
or	O
operand	O
size	O
.	O
</s>
<s>
These	O
principles	O
made	O
it	O
straightforward	O
to	O
find	O
names	O
and	O
forms	O
for	O
all	O
new	O
Z80	B-General_Concept
instructions	O
,	O
as	O
well	O
as	O
orthogonalizations	O
of	O
old	O
ones	O
,	O
such	O
as	O
LD	O
BC	O
,	O
(	O
1234	O
)	O
.	O
</s>
<s>
Apart	O
from	O
naming	O
differences	O
,	O
and	O
despite	O
a	O
certain	O
discrepancy	O
in	O
basic	O
register	O
structure	O
,	O
the	O
Z80	B-General_Concept
and	O
8086	B-General_Concept
syntax	O
are	O
virtually	O
isomorphic	O
for	O
a	O
large	O
portion	O
of	O
instructions	O
.	O
</s>
<s>
Only	O
quite	O
superficial	O
similarities	O
(	O
such	O
as	O
the	O
word	O
MOV	O
,	O
or	O
the	O
letter	O
X	O
,	O
for	O
extended	O
register	O
)	O
exist	O
between	O
the	O
8080	B-General_Concept
and	O
8086	B-General_Concept
assembly	B-Language
languages	I-Language
,	O
although	O
8080	B-General_Concept
programs	O
can	O
be	O
translated	O
to	O
8086	B-General_Concept
assembly	B-Language
language	I-Language
by	O
translator	O
programs	O
.	O
</s>
<s>
The	O
Z80	B-General_Concept
uses	O
252	O
out	O
of	O
the	O
available	O
256	O
codes	O
as	O
single	O
byte	O
opcodes	O
(	O
"	O
root	O
instruction	O
"	O
which	O
are	O
all	O
inherited	O
from	O
the	O
8080	B-General_Concept
)	O
;	O
the	O
four	O
remaining	O
codes	O
are	O
used	O
extensively	O
as	O
opcode	O
prefixes	O
:	O
CB	O
and	O
ED	O
enable	O
extra	O
instructions	O
,	O
and	O
DD	O
or	O
FD	O
select	O
IX+d	O
or	O
IY+d	O
respectively	O
(	O
in	O
some	O
cases	O
without	O
displacement	O
d	O
)	O
in	O
place	O
of	O
HL	O
.	O
</s>
<s>
This	O
scheme	O
gives	O
the	O
Z80	B-General_Concept
a	I-General_Concept
large	O
number	O
of	O
permutations	O
of	O
instructions	O
and	O
registers	O
;	O
Zilog	O
categorizes	O
these	O
into	O
158	O
different	O
"	O
instruction	O
types	O
"	O
,	O
78	O
of	O
which	O
are	O
the	O
same	O
as	O
those	O
of	O
the	O
Intel	B-General_Concept
8080	I-General_Concept
(	O
allowing	O
operation	O
of	O
all	O
8080	B-General_Concept
programs	O
on	O
a	O
Z80	B-General_Concept
)	O
.	O
</s>
<s>
The	O
Zilog	O
documentation	O
further	O
groups	O
instructions	O
into	O
the	O
following	O
categories	O
(	O
most	O
from	O
the	O
8080	B-General_Concept
,	O
others	O
entirely	O
new	O
like	O
the	O
block	O
and	O
bit	O
instructions	O
,	O
and	O
others	O
8080	B-General_Concept
instructions	O
with	O
more	O
versatile	O
addressing	B-Language
modes	I-Language
,	O
like	O
the	O
16-bit	O
loads	O
,	O
I/O	B-General_Concept
,	O
rotates/shifts	O
and	O
relative	O
jumps	O
)	O
:	O
</s>
<s>
No	O
explicit	O
multiply	O
instructions	O
are	O
available	O
in	O
the	O
original	O
Z80	B-General_Concept
,	O
though	O
registers	O
A	O
and	O
HL	O
can	O
be	O
multiplied	O
by	O
powers	O
of	O
two	O
with	O
ADDA	O
,	O
A	O
and	O
ADDHL	O
,	O
HL	O
instructions	O
(	O
similarly	O
IX	O
and	O
IY	O
also	O
)	O
.	O
</s>
<s>
Different	O
sizes	O
and	O
variants	O
of	O
additions	O
,	O
shifts	O
,	O
and	O
rotates	O
have	O
somewhat	O
differing	O
effects	O
on	O
flags	O
because	O
most	O
of	O
the	O
flag-changing	O
properties	O
of	O
the	O
8080	B-General_Concept
were	O
copied	O
.	O
</s>
<s>
However	O
,	O
the	O
parity	B-General_Concept
flag	I-General_Concept
bitP	O
of	O
the	O
8080	B-General_Concept
(	O
bit2	O
)	O
is	O
called	O
P/V	O
(	O
parity/overflow	O
)	O
in	O
the	O
Z80	B-General_Concept
as	I-General_Concept
it	O
serves	O
the	O
additional	O
purpose	O
of	O
a	O
twos	O
complement	O
overflow	O
indicator	O
,	O
a	O
feature	O
lacking	O
in	O
the	O
8080	B-General_Concept
.	O
</s>
<s>
Arithmetic	O
instructions	O
on	O
the	O
Z80	B-General_Concept
set	O
it	O
to	O
indicate	O
overflow	O
rather	O
than	O
parity	O
,	O
while	O
bitwise	O
instructions	O
still	O
use	O
it	O
as	O
a	O
parity	B-General_Concept
flag	I-General_Concept
.	O
</s>
<s>
(	O
This	O
introduces	O
a	O
subtle	O
incompatibility	O
of	O
the	O
Z80	B-General_Concept
with	O
code	O
written	O
for	O
the	O
8080	B-General_Concept
,	O
as	O
the	O
Z80	B-General_Concept
sometimes	O
indicates	O
signed	O
overflow	O
where	O
the	O
8080	B-General_Concept
would	O
indicate	O
parity	O
,	O
possibly	O
causing	O
the	O
logic	O
of	O
some	O
practical	O
8080	B-General_Concept
software	O
to	O
fail	O
on	O
the	O
Z80	B-General_Concept
.	O
)	O
</s>
<s>
This	O
new	O
overflow	B-Algorithm
flag	I-Algorithm
is	O
used	O
for	O
all	O
new	O
Z80-specific	O
16-bit	O
operations	O
(	O
,	O
)	O
as	O
well	O
as	O
for	O
8-bit	O
arithmetic	O
operations	O
,	O
while	O
the	O
16-bit	O
operations	O
inherited	O
from	O
the	O
8080	B-General_Concept
(	O
,	O
,	O
)	O
do	O
not	O
affect	O
it	O
.	O
</s>
<s>
Also	O
,	O
bit1	O
of	O
the	O
flags	O
register	O
(	O
a	O
spare	O
bit	O
on	O
the	O
8080	B-General_Concept
)	O
is	O
used	O
as	O
a	O
flagN	O
that	O
indicates	O
whether	O
the	O
last	O
arithmetic	O
instruction	O
executed	O
was	O
a	O
subtraction	O
or	O
addition	O
.	O
</s>
<s>
The	O
Z80	B-General_Concept
version	O
of	O
the	O
instruction	O
(	O
decimal	O
adjust	O
accumulator	B-General_Concept
for	O
BCD	O
arithmetic	O
)	O
checks	O
the	O
Nflag	O
and	O
behaves	O
accordingly	O
,	O
so	O
a	O
(	O
hypothetical	O
)	O
subtraction	O
followed	O
later	O
by	O
will	O
yield	O
a	O
different	O
result	O
on	O
an	O
old	O
8080	B-General_Concept
than	O
on	O
the	O
Z80	B-General_Concept
.	O
</s>
<s>
However	O
,	O
this	O
would	O
likely	O
be	O
erroneous	O
code	O
on	O
the	O
8080	B-General_Concept
,	O
as	O
was	O
defined	O
for	O
addition	O
only	O
on	O
that	O
processor	O
.	O
</s>
<s>
The	O
Z80	B-General_Concept
has	O
six	O
new	O
instructions	O
that	O
can	O
load	O
the	O
DE	O
,	O
BC	O
,	O
and	O
SP	O
register	O
pairs	O
from	O
memory	O
,	O
and	O
load	O
memory	O
from	O
these	O
three	O
register	O
pairs	O
—	O
unlike	O
the	O
8080	B-General_Concept
.	O
</s>
<s>
As	O
on	O
the	O
8080	B-General_Concept
,	O
load	O
instructions	O
do	O
not	O
affect	O
the	O
flags	O
(	O
except	O
for	O
the	O
special-purpose	O
I	O
and	O
R	O
register	O
loads	O
)	O
.	O
</s>
<s>
A	O
result	O
of	O
a	O
regular	O
encoding	O
(	O
common	O
with	O
the	O
8080	B-General_Concept
)	O
is	O
that	O
each	O
of	O
the	O
8-bit	O
registers	O
can	O
be	O
loaded	O
from	O
themselves	O
(	O
e.g.	O
</s>
<s>
New	O
block	O
transfer	O
instructions	O
can	O
move	O
up	O
to	O
64kilobytes	O
from	O
memory	O
to	O
memory	O
or	O
between	O
memory	O
and	O
I/O	B-General_Concept
peripheral	O
ports	O
.	O
</s>
<s>
Non-repeating	O
versions	O
and	O
move	O
a	O
single	O
byte	O
and	O
bump	O
the	O
pointers	O
and	O
byte	O
counter	O
,	O
which	O
if	O
it	O
becomes	O
zero	O
resets	O
the	O
P/Vflag	O
.	O
</s>
<s>
Corresponding	O
memory-to-I/O	O
instructions	O
,	O
,	O
,	O
,	O
,	O
,	O
and	O
operate	O
similarly	O
.	O
</s>
<s>
The	O
Z80	B-General_Concept
can	O
input	B-General_Concept
and	I-General_Concept
output	I-General_Concept
any	O
register	O
to	O
an	O
I/O	B-Architecture
port	I-Architecture
using	O
registerC	O
to	O
designate	O
the	O
port	O
.	O
</s>
<s>
(	O
The	O
8080	B-General_Concept
only	O
performs	O
I/O	B-General_Concept
through	O
the	O
accumulatorA	O
,	O
using	O
a	O
direct	O
port	O
address	O
specified	O
in	O
the	O
instruction	O
;	O
a	O
self-modifying	B-Application
code	I-Application
technique	O
is	O
required	O
to	O
use	O
a	O
variable	O
8080	B-General_Concept
port	O
address	O
.	O
)	O
</s>
<s>
Unlike	O
the	O
8080	B-General_Concept
,	O
the	O
Z80	B-General_Concept
can	O
jump	O
to	O
a	O
relative	B-General_Concept
address	I-General_Concept
(	O
instead	O
of	O
)	O
using	O
a	O
signed	O
8-bit	O
displacement	O
.	O
</s>
<s>
Only	O
the	O
zero	O
and	O
carry	B-Algorithm
flags	I-Algorithm
can	O
be	O
tested	O
for	O
these	O
new	O
two-byte	O
instructions	O
.	O
</s>
<s>
(	O
All	O
8080	B-General_Concept
jumps	O
and	O
calls	O
,	O
conditional	O
or	O
not	O
,	O
are	O
three-byte	O
instructions	O
.	O
)	O
</s>
<s>
A	O
two-byte	O
instruction	O
specialized	O
for	O
program	O
looping	O
is	O
also	O
new	O
to	O
the	O
Z80	B-General_Concept
:	O
(	O
decrement	O
jump	O
if	O
non-zero	O
)	O
takes	O
a	O
signed	O
8-bit	O
displacement	O
as	O
an	O
immediate	O
operand	O
.	O
</s>
<s>
To	O
perform	O
an	O
equivalent	O
loop	O
on	O
an	O
8080	B-General_Concept
requires	O
separate	O
and	O
conditional	O
jump	O
(	O
to	O
a	O
two-byte	O
absolute	O
address	O
)	O
instructions	O
(	O
totalling	O
four	O
bytes	O
)	O
,	O
and	O
the	O
alters	O
the	O
flag	O
register	O
.	O
</s>
<s>
The	O
index	B-General_Concept
register	I-General_Concept
(	O
IX/IY	O
,	O
often	O
abbreviated	O
XY	O
)	O
instructions	O
can	O
be	O
useful	O
for	O
accessing	O
data	O
organised	O
in	O
fixed	O
heterogenous	O
structures	O
(	O
such	O
as	O
records	O
)	O
or	O
at	O
fixed	O
offsets	B-General_Concept
relative	O
a	O
variable	O
base	O
address	O
(	O
as	O
in	O
recursive	O
stack	O
frames	O
)	O
and	O
can	O
also	O
reduce	O
code	O
size	O
by	O
removing	O
the	O
need	O
for	O
multiple	O
short	O
instructions	O
using	O
non-indexed	O
registers	O
.	O
</s>
<s>
Thus	O
,	O
for	O
simple	O
or	O
linear	B-General_Concept
accesses	O
of	O
data	O
,	O
use	O
of	O
IX	O
and	O
IY	O
tend	O
to	O
be	O
slower	O
and	O
occupy	O
more	O
memory	O
.	O
</s>
<s>
Similarly	O
,	O
instructions	O
for	O
16-bit	O
additions	O
are	O
not	O
particularly	O
fast	O
(	O
11clocks	O
)	O
in	O
the	O
original	O
Z80	B-General_Concept
(	O
being	O
1clock	O
slower	O
than	O
in	O
the	O
8080/8085	O
)	O
;	O
nonetheless	O
,	O
they	O
are	O
about	O
twice	O
as	O
fast	O
as	O
performing	O
the	O
same	O
calculations	O
using	O
8-bit	O
operations	O
,	O
and	O
equally	O
important	O
,	O
they	O
reduce	O
register	O
usage	O
.	O
</s>
<s>
It	O
was	O
not	O
uncommon	O
for	O
programmers	O
to	O
"	O
poke	O
"	O
different	O
offset	B-General_Concept
displacement	O
bytes	O
(	O
which	O
were	O
typically	O
calculated	O
dynamically	O
)	O
into	O
indexed	O
instructions	O
;	O
this	O
is	O
an	O
example	O
of	O
self-modifying	B-Application
code	I-Application
,	O
which	O
was	O
regular	O
practice	O
on	O
nearly	O
all	O
early	O
8-bit	O
processors	O
with	O
non-pipelined	O
execution	O
units	O
.	O
</s>
<s>
The	O
index	B-General_Concept
registers	I-General_Concept
have	O
a	O
parallel	O
instruction	O
to	O
,	O
which	O
is	O
.	O
</s>
<s>
This	O
is	O
often	O
seen	O
in	O
stack-oriented	O
languages	O
like	O
Forth	B-Application
,	O
which	O
at	O
the	O
end	O
of	O
every	O
Forth	B-Application
word	O
(	O
atomic	O
subroutines	O
comprising	O
the	O
language	O
)	O
must	O
jump	O
unconditionally	O
back	O
to	O
their	O
thread	O
interpreter	O
routines	O
.	O
</s>
<s>
This	O
naturally	O
makes	O
the	O
index	B-General_Concept
register	I-General_Concept
unavailable	O
for	O
any	O
other	O
use	O
,	O
or	O
else	O
the	O
need	O
to	O
constantly	O
reload	O
it	O
would	O
negate	O
its	O
efficiency	O
.	O
</s>
<s>
The	O
10-year-newer	O
microcoded	O
Z180	B-Device
design	B-Architecture
could	O
initially	O
afford	O
more	O
"	O
chip	O
area	O
"	O
,	O
permitting	O
a	O
slightly	O
more	O
efficient	O
implementation	O
(	O
using	O
a	O
wider	O
ALU	B-General_Concept
,	O
among	O
other	O
things	O
)	O
;	O
similar	O
things	O
can	O
be	O
said	O
for	O
the	O
Z800	B-Device
,	O
Z280	B-Device
,	O
and	O
Z380	B-Device
.	O
</s>
<s>
However	O
,	O
it	O
was	O
not	O
until	O
the	O
fully	O
pipelined	B-General_Concept
eZ80	B-Device
was	O
launched	O
in	O
2001	O
that	O
those	O
instructions	O
finally	O
became	O
approximately	O
as	O
cycle-efficient	O
as	O
it	O
is	O
technically	O
possible	O
to	O
make	O
them	O
,	O
i.e.	O
</s>
<s>
given	O
the	O
Z80	B-General_Concept
encodings	O
combined	O
with	O
the	O
capability	O
to	O
do	O
an	O
8-bit	O
read	O
or	O
write	O
every	O
clock	O
cycle	O
.	O
</s>
<s>
The	O
index	B-General_Concept
registers	I-General_Concept
,	O
IX	O
and	O
IY	O
,	O
were	O
intended	O
as	O
flexible	O
16-bit	O
pointers	O
,	O
enhancing	O
the	O
ability	O
to	O
manipulate	O
memory	O
,	O
stack	O
frames	O
and	O
data	O
structures	O
.	O
</s>
<s>
Zilog	O
published	O
the	O
opcodes	O
and	O
related	O
mnemonics	O
for	O
the	O
intended	O
functions	O
,	O
but	O
did	O
not	O
document	O
the	O
fact	O
that	O
every	O
opcode	O
that	O
allowed	O
manipulation	O
of	O
the	O
H	B-Application
and	O
L	O
registers	O
was	O
equally	O
valid	O
for	O
the	O
8	O
bit	O
portions	O
of	O
the	O
IX	O
and	O
IY	O
registers	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
opcode	O
26h	O
followed	O
by	O
an	O
immediate	O
byte	O
value	O
will	O
load	O
that	O
value	O
into	O
the	O
H	B-Application
register	O
.	O
</s>
<s>
Preceding	O
this	O
two-byte	O
instruction	O
with	O
the	O
IX	O
register	O
's	O
opcode	O
prefix	O
,	O
DD	O
,	O
would	O
instead	O
result	O
in	O
the	O
most	O
significant	O
8	O
bits	O
of	O
the	O
IX	O
register	O
being	O
loaded	O
with	O
that	O
same	O
value	O
.	O
</s>
<s>
The	O
undocumented	O
ability	O
to	O
increment	O
and	O
decrement	O
the	O
upper	O
half	O
of	O
an	O
index	B-General_Concept
register	I-General_Concept
made	O
it	O
easy	O
to	O
expand	O
the	O
range	O
of	O
the	O
normal	O
indexed	O
instructions	O
,	O
without	O
having	O
to	O
resort	O
to	O
the	O
documented	O
or	O
.	O
</s>
<s>
There	O
are	O
several	O
other	O
undocumented	B-Language
instructions	I-Language
as	O
well	O
.	O
</s>
<s>
Undocumented	O
or	O
illegal	B-Language
opcodes	I-Language
are	O
not	O
detected	O
by	O
the	O
Z80	B-General_Concept
and	O
have	O
various	O
effects	O
,	O
some	O
of	O
which	O
are	O
useful	O
.	O
</s>
<s>
However	O
,	O
as	O
they	O
are	O
not	O
part	O
of	O
the	O
formal	O
definition	O
of	O
the	O
instruction	B-General_Concept
set	I-General_Concept
,	O
different	O
implementations	O
of	O
the	O
Z80	B-General_Concept
are	O
not	O
guaranteed	O
(	O
or	O
especially	O
likely	O
)	O
to	O
work	O
the	O
same	O
way	O
for	O
every	O
undocumented	B-Language
opcode	I-Language
.	O
</s>
<s>
The	O
instruction	O
does	O
not	O
conform	O
to	O
the	O
Z80	B-General_Concept
documentation	O
.	O
</s>
<s>
Both	O
the	O
and	O
instructions	O
are	O
supposed	O
to	O
leave	O
the	O
carry	O
(	O
C	B-Algorithm
)	O
flag	O
unmodified	O
.	O
</s>
<s>
The	O
instruction	O
operates	O
correctly	O
;	O
however	O
,	O
during	O
the	O
execution	O
of	O
the	O
instruction	O
,	O
the	O
carry	B-Algorithm
flag	I-Algorithm
takes	O
the	O
results	O
of	O
a	O
spurious	O
compare	O
between	O
the	O
accumulator	B-General_Concept
(	O
A	O
)	O
and	O
the	O
last	O
output	O
of	O
the	O
instruction	O
.	O
</s>
<s>
The	O
following	O
Z80	B-General_Concept
assembler	B-Language
source	O
code	O
is	O
for	O
a	O
subroutine	O
named	O
HELLO_WORLD	O
.	O
</s>
<s>
Though	O
simple	O
,	O
it	O
demonstrates	O
how	O
an	O
assembler	B-Language
source	O
code	O
is	O
formatted	O
and	O
interacts	O
with	O
the	O
display	O
hardware	O
through	O
a	O
computer	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
.	O
</s>
<s>
This	O
is	O
necessarily	O
specific	O
to	O
a	O
particular	O
computer	O
hardware	O
,	O
operating	B-General_Concept
system	I-General_Concept
and	O
assembler	B-Language
software	O
.	O
</s>
<s>
The	O
example	O
used	O
is	O
the	O
TRS-80	B-Device
Model	I-Device
4	I-Device
running	O
TRSDOS/LS	O
-DOS	O
6.x	O
,	O
produced	O
by	O
Tandy/Radio	O
Shack	O
and	O
Logical	O
Systems	O
,	O
with	O
most	O
any	O
assembler	B-Language
sold	O
by	O
Radio	O
Shack	O
or	O
Misosys	O
Inc	O
.	O
(	O
Series	O
I/EDTASM	O
,	O
ALDS	O
,	O
EDAS	O
or	O
MRAS	O
with	O
-GC	O
switch	O
)	O
.	O
</s>
<s>
The	O
principal	O
features	O
of	O
this	O
configuration	O
are	O
universal	O
to	O
Z80	B-General_Concept
assemblers	B-Language
,	O
even	O
under	O
CP/M	B-Application
.	O
</s>
<s>
The	O
following	O
Z80	B-General_Concept
assembly	O
source	O
code	O
is	O
for	O
a	O
subroutine	O
named	O
memcpy	O
that	O
copies	O
a	O
block	O
of	O
data	O
bytes	O
of	O
a	O
given	O
size	O
from	O
one	O
location	O
to	O
another	O
.	O
</s>
<s>
Important	O
:	O
the	O
example	O
code	O
does	O
not	O
handle	O
the	O
case	O
where	O
the	O
destination	O
block	O
overlaps	O
the	O
source	O
;	O
a	O
serious	O
limitation	O
,	O
but	O
one	O
that	O
is	O
irrelevant	O
for	O
some	O
applications	O
—	O
such	O
as	O
,	O
especially	O
,	O
when	O
the	O
source	O
is	O
in	O
ROM	B-Device
and	O
the	O
destination	O
in	O
RAM	O
,	O
so	O
they	O
can	O
never	O
overlap	O
.	O
</s>
<s>
Furthermore	O
,	O
the	O
Z80	B-General_Concept
has	O
a	O
single	O
instruction	O
that	O
will	O
execute	O
the	O
entire	O
loop	O
(	O
LDIR	O
)	O
.	O
</s>
<s>
Note	O
that	O
the	O
assembled	O
code	O
is	O
binary-compatible	B-General_Concept
with	O
the	O
Intel	B-General_Concept
8080	I-General_Concept
and	O
8085	B-General_Concept
CPUs	B-General_Concept
.	O
</s>
<s>
or	O
c	B-Algorithm
;	O
If	O
BC	O
=	O
0	O
,	O
</s>
<s>
Each	O
instruction	O
is	O
executed	O
in	O
steps	O
that	O
are	O
usually	O
termed	O
machine	B-General_Concept
cycles	I-General_Concept
(	O
M-cycles	O
)	O
,	O
each	O
of	O
which	O
can	O
take	O
between	O
three	O
and	O
six	O
clock	O
periods	O
(	O
T-states	O
)	O
.	O
</s>
<s>
The	O
Z80	B-General_Concept
machine	B-General_Concept
cycles	I-General_Concept
are	O
sequenced	O
by	O
an	O
internal	O
state	B-Architecture
machine	I-Architecture
which	O
builds	O
each	O
M-cycle	O
out	O
of	O
3	O
,	O
4	O
,	O
5	O
or	O
6	O
T-states	O
depending	O
on	O
context	O
.	O
</s>
<s>
It	O
also	O
means	O
that	O
a	O
higher	O
frequency	O
crystal	O
must	O
be	O
used	O
than	O
without	O
this	O
subdivision	O
of	O
machine	B-General_Concept
cycles	I-General_Concept
(	O
approximately	O
2	O
–	O
3	O
times	O
higher	O
)	O
.	O
</s>
<s>
It	O
does	O
not	O
imply	O
tighter	O
requirements	O
on	O
memory	B-Architecture
access	I-Architecture
times	I-Architecture
,	O
since	O
a	O
high	O
resolution	O
clock	O
allows	O
more	O
precise	O
control	O
of	O
memory	O
timings	O
and	O
so	O
memory	O
can	O
be	O
active	O
in	O
parallel	O
with	O
the	O
CPU	O
to	O
a	O
greater	O
extent	O
,	O
allowing	O
more	O
efficient	O
use	O
of	O
available	O
memory	O
bandwidth	O
.	O
</s>
<s>
One	O
central	O
example	O
of	O
this	O
is	O
that	O
,	O
for	O
opcode	O
fetch	O
,	O
the	O
Z80	B-General_Concept
combines	O
two	O
full	O
clock	O
cycles	O
into	O
a	O
memory	O
access	O
period	O
(	O
the	O
M1-signal	O
)	O
.	O
</s>
<s>
In	O
the	O
Z80	B-General_Concept
this	O
signal	O
lasts	O
for	O
a	O
relatively	O
larger	O
part	O
of	O
the	O
typical	O
instruction	O
execution	O
time	O
than	O
in	O
a	O
design	B-Architecture
such	O
as	O
the	O
6800	B-Device
,	O
6502	B-General_Concept
,	O
or	O
similar	O
,	O
where	O
this	O
period	O
would	O
typically	O
last	O
typically	O
30-40	O
%	O
of	O
a	O
clock	O
cycle	O
.	O
</s>
<s>
lower	O
internal	O
clock	O
speed	O
)	O
than	O
the	O
Z80	B-General_Concept
.	O
</s>
<s>
Memory	O
was	O
generally	O
slow	O
compared	O
to	O
the	O
state	B-Architecture
machine	I-Architecture
sub-cycles	O
(	O
clock	O
cycles	O
)	O
used	O
in	O
contemporary	O
microprocessors	B-Architecture
.	O
</s>
<s>
The	O
shortest	O
machine	B-General_Concept
cycle	I-General_Concept
that	O
could	O
safely	O
be	O
used	O
in	O
embedded	O
designs	O
has	O
therefore	O
often	O
been	O
limited	O
by	O
memory	B-Architecture
access	I-Architecture
times	I-Architecture
,	O
not	O
by	O
the	O
maximum	O
CPU	O
frequency	O
(	O
especially	O
so	O
during	O
the	O
home	O
computer	O
era	O
)	O
.	O
</s>
<s>
However	O
,	O
this	O
relation	O
has	O
slowly	O
changed	O
during	O
the	O
last	O
decades	O
,	O
particularly	O
regarding	O
SRAM	B-Architecture
;	O
cacheless	O
,	O
single-cycle	O
designs	O
such	O
as	O
the	O
eZ80	B-Device
have	O
therefore	O
become	O
much	O
more	O
meaningful	O
recently	O
.	O
</s>
<s>
The	O
content	O
of	O
the	O
refresh	B-General_Concept
register	O
R	O
is	O
sent	O
out	O
on	O
the	O
lower	O
half	O
of	O
the	O
address	O
bus	O
along	O
with	O
a	O
refresh	B-General_Concept
control	O
signal	O
while	O
the	O
CPU	O
is	O
decoding	O
and	O
executing	O
the	O
fetched	O
instruction	O
.	O
</s>
<s>
During	O
refresh	B-General_Concept
the	O
contents	O
of	O
the	O
Interrupt	B-Application
register	O
I	O
are	O
sent	O
out	O
on	O
the	O
upper	O
half	O
of	O
the	O
address	O
bus	O
.	O
</s>
<s>
Zilog	O
introduced	O
a	O
number	O
of	O
peripheral	O
parts	O
for	O
the	O
Z80	B-General_Concept
,	O
which	O
all	O
support	O
the	O
Z80	B-General_Concept
's	O
interrupt	B-Application
handling	I-Application
system	O
and	O
I/O	B-Architecture
address	I-Architecture
space	O
.	O
</s>
<s>
These	O
include	O
the	O
counter/timer	O
channel	O
(	O
CTC	O
)	O
,	O
the	O
SIO	O
(	O
serial	O
input/output	B-General_Concept
)	O
,	O
the	O
DMA	O
(	O
direct	O
memory	O
access	O
)	O
,	O
the	O
PIO	O
(	O
parallel	O
input/output	B-General_Concept
)	O
and	O
the	O
DART	O
(	O
dual	O
asynchronous	O
receiver	O
–	O
transmitter	O
)	O
.	O
</s>
<s>
As	O
the	O
product	O
line	O
developed	O
,	O
low-power	O
,	O
high-speed	O
and	O
CMOS	B-Device
versions	O
of	O
these	O
chips	O
were	O
introduced	O
.	O
</s>
<s>
Like	O
the	O
8080	B-General_Concept
,	O
8085	B-General_Concept
and	O
8086	B-General_Concept
processors	O
,	O
but	O
unlike	O
processors	O
such	O
as	O
the	O
Motorola	B-Device
6800	I-Device
and	O
MOS	B-General_Concept
Technology	I-General_Concept
6502	I-General_Concept
,	O
the	O
Z80	B-General_Concept
and	O
8080	B-General_Concept
has	O
a	O
separate	O
control	O
line	O
and	O
address	B-General_Concept
space	I-General_Concept
for	O
I/O	B-General_Concept
instructions	O
.	O
</s>
<s>
While	O
some	O
Z80-based	O
computers	O
such	O
as	O
the	O
Osborne	B-Device
1	I-Device
used	O
"	O
Motorola-style	O
"	O
memory	B-Architecture
mapped	I-Architecture
input/output	I-Architecture
devices	O
,	O
usually	O
the	O
I/O	B-General_Concept
space	O
was	O
used	O
to	O
address	O
one	O
of	O
the	O
many	O
Zilog	O
peripheral	O
chips	O
compatible	O
with	O
the	O
Z80	B-General_Concept
.	O
</s>
<s>
Zilog	O
I/O	B-General_Concept
chips	O
supported	O
the	O
Z80	B-General_Concept
's	O
new	O
mode	O
2	O
interrupts	B-Application
which	O
simplified	O
interrupt	B-Application
handling	I-Application
for	O
large	O
numbers	O
of	O
peripherals	O
.	O
</s>
<s>
The	O
Z80	B-General_Concept
was	O
officially	O
described	O
as	O
supporting	O
16-bit	O
(	O
64KB	O
)	O
memory	O
addressing	O
,	O
and	O
8-bit	O
(	O
256	O
ports	O
)	O
I/O	B-General_Concept
-addressing	O
.	O
</s>
<s>
All	O
I/O	B-General_Concept
instructions	O
actually	O
assert	O
the	O
entire	O
16-bit	O
address	O
bus	O
.	O
</s>
<s>
OUT(C )	O
,	O
reg	O
and	O
INreg	O
,	O
(	O
C	B-Algorithm
)	O
places	O
the	O
contents	O
of	O
the	O
entire	O
16-bit	O
BC	O
register	O
on	O
the	O
address	O
bus	O
;	O
OUT(n )	O
,	O
A	O
and	O
INA	O
,	O
(	O
n	O
)	O
places	O
the	O
contents	O
of	O
the	O
Aregister	O
on	O
b8	O
–	O
b15	O
of	O
the	O
address	O
bus	O
and	O
n	O
on	O
b0	O
–	O
b7	O
of	O
the	O
address	O
bus	O
.	O
</s>
<s>
A	O
designer	O
could	O
choose	O
to	O
decode	O
the	O
entire	O
16-bit	O
address	O
bus	O
on	O
I/O	B-General_Concept
operations	I-General_Concept
in	O
order	O
to	O
take	O
advantage	O
of	O
this	O
feature	O
,	O
or	O
use	O
the	O
high	O
half	O
of	O
the	O
address	O
bus	O
to	O
select	O
subfeatures	O
of	O
the	O
I/O	B-General_Concept
device	I-General_Concept
.	O
</s>
<s>
This	O
feature	O
has	O
also	O
been	O
used	O
to	O
minimise	O
decoding	O
hardware	O
requirements	O
,	O
such	O
as	O
in	O
the	O
Amstrad	O
CPC/PCW	O
and	O
ZX81	O
.	O
</s>
<s>
Mostek	O
,	O
which	O
produced	O
the	O
first	O
Z80	B-General_Concept
for	O
Zilog	O
,	O
offered	O
it	O
as	O
second-source	O
as	O
MK3880	O
.	O
</s>
<s>
Sharp	O
and	O
NEC	O
developed	O
second	O
sources	O
for	O
the	O
NMOS	B-Algorithm
Z80	B-General_Concept
,	O
the	O
LH0080	O
and	O
μPD780C	O
,	O
respectively	O
.	O
</s>
<s>
The	O
LH0080	O
was	O
used	O
in	O
various	O
home	O
computers	O
and	O
personal	O
computers	O
made	O
by	O
Sharp	O
and	O
other	O
Japanese	O
manufacturers	O
,	O
including	O
Sony	O
MSX	B-Operating_System
computers	I-Operating_System
,	O
and	O
a	O
number	O
of	O
computers	O
in	O
the	O
Sharp	B-Operating_System
MZ	I-Operating_System
series	O
.	O
</s>
<s>
Toshiba	O
made	O
a	O
CMOS-version	O
,	O
the	O
TMPZ84C00	O
,	O
which	O
is	O
believed	O
(	O
but	O
not	O
verified	O
)	O
to	O
be	O
the	O
same	O
design	B-Architecture
also	O
used	O
by	O
Zilog	O
for	O
its	O
own	O
CMOS	B-Device
Z84C00	O
.	O
</s>
<s>
There	O
were	O
also	O
Z80-chips	O
made	O
by	O
GoldStar	O
(	O
now	O
LG	O
)	O
and	O
the	O
BU18400	O
series	O
of	O
Z80-clones	O
(	O
including	O
DMA	O
,	O
PIO	O
,	O
CTC	O
,	O
DART	O
and	O
SIO	O
)	O
in	O
NMOS	B-Algorithm
and	O
CMOS	B-Device
made	O
by	O
ROHM	O
Electronics	O
.	O
</s>
<s>
In	O
East	O
Germany	O
,	O
an	O
unlicensed	O
clone	O
of	O
the	O
Z80	B-General_Concept
,	O
known	O
as	O
the	O
U880	B-Device
,	O
was	O
manufactured	O
.	O
</s>
<s>
It	O
was	O
used	O
extensively	O
in	O
Robotron	O
's	O
and	O
VEB	O
Mikroelektronik	O
Mühlhausen	O
's	O
computer	O
systems	O
(	O
such	O
as	O
the	O
KC85-series	O
)	O
and	O
also	O
in	O
many	O
self-made	O
computer	O
systems	O
.	O
</s>
<s>
In	O
Romania	O
another	O
unlicensed	O
clone	O
could	O
be	O
found	O
,	O
named	O
MMN80CPU	B-General_Concept
and	O
produced	O
by	O
Microelectronica	O
,	O
used	O
in	O
home	O
computers	O
like	O
TIM-S	O
,	O
HC	O
,	O
COBRA	O
.	O
</s>
<s>
Also	O
,	O
several	O
clones	O
of	O
Z80	B-General_Concept
were	O
created	O
in	O
the	O
Soviet	O
Union	O
,	O
notable	O
ones	O
being	O
the	O
T34BM1	O
,	O
also	O
called	O
КР1858ВМ1	O
(	O
parallelling	O
the	O
Soviet	O
8080-clone	O
KR580VM80A	O
)	O
.	O
</s>
<s>
Hitachi	O
developed	O
the	O
HD64180	B-General_Concept
,	O
a	O
microcoded	O
and	O
partially	O
dynamic	O
Z80	B-General_Concept
in	O
CMOS	B-Device
,	O
with	O
on	O
chip	O
peripherals	O
and	O
a	O
simple	O
MMU	O
giving	O
a	O
1MB	O
address	B-General_Concept
space	I-General_Concept
.	O
</s>
<s>
It	O
was	O
later	O
second	O
sourced	O
by	O
Zilog	O
,	O
initially	O
as	O
the	O
Z64180	B-General_Concept
,	O
and	O
then	O
in	O
the	O
form	O
of	O
the	O
slightly	O
modified	O
Z180	B-Device
which	O
has	O
bus	O
protocol	O
and	O
timings	O
better	O
adapted	O
to	O
Z80	B-General_Concept
peripheral	O
chips	O
.	O
</s>
<s>
Z180	B-Device
has	O
been	O
maintained	O
and	O
further	O
developed	O
under	O
Zilog	O
's	O
name	O
,	O
the	O
newest	O
versions	O
being	O
based	O
on	O
the	O
fully	O
static	O
S180/L180	O
core	O
with	O
very	O
low	O
power	O
draw	O
and	O
EMI	O
(	O
noise	O
)	O
.	O
</s>
<s>
Toshiba	O
developed	O
the	O
84	O
pin	O
Z84013	O
/	O
Z84C13	O
and	O
the	O
100	O
pin	O
Z84015	O
/	O
Z84C15	O
series	O
of	O
"	O
intelligent	O
peripheral	O
controllers	O
"	O
,	O
basically	O
ordinary	O
NMOS	B-Algorithm
and	O
CMOS	B-Device
Z80	B-General_Concept
cores	O
with	O
Z80	B-General_Concept
peripherals	O
,	O
watchdog	B-Application
timer	I-Application
,	O
power	B-Application
on	I-Application
reset	I-Application
,	O
and	O
wait	O
state	O
generator	O
on	O
the	O
same	O
chip	O
.	O
</s>
<s>
The	O
32-bit	O
Z80	B-General_Concept
compatible	O
Zilog	B-Device
Z380	I-Device
,	O
introduced	O
1994	O
,	O
is	O
used	O
mainly	O
in	O
telecom	O
equipment	O
.	O
</s>
<s>
Zilog	O
's	O
fully	O
pipelined	B-General_Concept
Z80	B-General_Concept
compatible	O
eZ80	B-Device
with	O
an	O
8/16/24	O
-bit	O
word	O
length	O
and	O
a	O
linear	B-General_Concept
16MB	O
address	B-General_Concept
space	I-General_Concept
was	O
introduced	O
in	O
2001	O
.	O
</s>
<s>
It	O
exists	O
in	O
versions	O
with	O
on	O
chip	O
SRAM	B-Architecture
or	O
flash	B-Device
memory	I-Device
,	O
as	O
well	O
as	O
with	O
integrated	O
peripherals	O
.	O
</s>
<s>
One	O
variant	O
has	O
on	O
chip	O
MAC	O
(	O
media	B-Protocol
access	I-Protocol
controller	I-Protocol
)	O
,	O
and	O
available	O
software	O
include	O
a	O
TCP/IP	B-Protocol
stack	I-Protocol
.	O
</s>
<s>
In	O
contrast	O
with	O
the	O
Z800	B-Device
and	O
Z280	B-Device
,	O
there	O
are	O
only	O
a	O
few	O
added	O
instructions	O
(	O
primarily	O
LEAs	O
,	O
PEAs	O
,	O
and	O
variable-address	O
16/24	O
-bit	O
loads	O
)	O
,	O
but	O
instructions	O
are	O
instead	O
executed	O
between	O
2	O
and	O
11	O
times	O
as	O
clock	O
cycle	O
efficient	O
as	O
on	O
the	O
original	O
Z80	B-General_Concept
(	O
with	O
a	O
mean	O
value	O
around	O
3-5	O
times	O
)	O
.	O
</s>
<s>
Kawasaki	O
developed	O
the	O
binary	B-General_Concept
compatible	I-General_Concept
KL5C8400	O
which	O
is	O
approximately	O
1.2-1.3	O
times	O
as	O
clock	O
cycle	O
efficient	O
as	O
the	O
original	O
Z80	B-General_Concept
and	O
can	O
be	O
clocked	O
at	O
up	O
to	O
33MHz	O
.	O
</s>
<s>
Kawasaki	O
also	O
produces	O
the	O
KL5C80A1x	O
family	O
,	O
which	O
has	O
peripherals	O
as	O
well	O
as	O
a	O
small	O
RAM	O
on	O
chip	O
;	O
it	O
is	O
approximately	O
as	O
clock	O
cycle	O
efficient	O
as	O
the	O
eZ80	B-Device
and	O
can	O
be	O
clocked	O
at	O
up	O
to	O
10MHz	O
(	O
2006	O
)	O
.	O
</s>
<s>
The	O
NEC	O
μPD9002	O
was	O
a	O
hybrid	O
CPU	O
compatible	O
with	O
both	O
Z80	B-General_Concept
and	O
x86	B-Operating_System
families	O
.	O
</s>
<s>
The	O
Chinese	O
Actions	O
Semiconductor	O
's	O
audio	O
processor	O
family	O
of	O
chips	O
(	O
ATJ2085	O
and	O
others	O
)	O
contains	O
a	O
Z80-compatible	O
MCUs	B-Architecture
together	O
with	O
a	O
24-bit	O
dedicated	O
DSP	O
processor	O
.	O
</s>
<s>
The	O
National	O
Semiconductor	O
NSC800	O
announced	O
in	O
1980	O
is	O
used	O
in	O
many	O
TeleSecurity	O
Timmann	O
(	O
TST	O
)	O
electronic	O
cipher	O
machines	O
and	O
the	O
Canon	B-Device
X-07	I-Device
.	O
</s>
<s>
The	O
NSC800	O
is	O
fully	O
compatible	O
with	O
the	O
Z-80	B-General_Concept
instruction	B-General_Concept
set	I-General_Concept
.	O
</s>
<s>
The	O
NSC800	O
uses	O
a	O
multiplexed	O
bus	O
like	O
the	O
8085	B-General_Concept
but	O
has	O
a	O
different	O
pinout	O
than	O
the	O
Z80	B-General_Concept
.	O
</s>
<s>
The	O
Toshiba	B-Device
TLCS	I-Device
900	O
series	O
of	O
high	O
volume	O
(	O
mostly	O
OTP	B-General_Concept
)	O
microcontrollers	B-Architecture
are	O
based	O
on	O
the	O
Z80	B-General_Concept
;	O
they	O
share	O
the	O
same	O
basic	O
BC	O
,	O
DE	O
,	O
HL	O
,	O
IX	O
,	O
IY	O
register	O
structure	O
,	O
and	O
largely	O
the	O
same	O
instructions	O
,	O
but	O
are	O
not	O
binary	B-General_Concept
compatible	I-General_Concept
,	O
while	O
the	O
previous	O
TLCS	O
90	O
is	O
Z80-compatible	O
.	O
</s>
<s>
The	O
NEC	B-Device
78K	I-Device
series	O
microcontrollers	B-Architecture
are	O
based	O
on	O
the	O
Z80	B-General_Concept
;	O
they	O
share	O
the	O
same	O
basic	O
BC	O
,	O
DE	O
,	O
HL	O
register	O
structure	O
,	O
and	O
has	O
similar	O
(	O
but	O
differently	O
named	O
)	O
instructions	O
;	O
not	O
binary	B-General_Concept
compatible	I-General_Concept
.	O
</s>
<s>
Rabbit	O
Semiconductor	O
's	O
Rabbit	B-Device
2000/3000/4000	I-Device
microprocessors/microcontrollers	O
are	O
based	O
on	O
the	O
HD64180/Z180	O
architecture	O
,	O
although	O
they	O
are	O
not	O
fully	O
binary	B-General_Concept
compatible	I-General_Concept
.	O
</s>
<s>
The	O
ASCII	B-General_Concept
Corporation	I-General_Concept
R800	I-General_Concept
was	O
a	O
fast	O
16-bit	O
processor	O
used	O
in	O
MSX	B-Operating_System
TurboR	I-Operating_System
computers	O
;	O
it	O
was	O
software-	O
,	O
but	O
not	O
hardware-compatible	O
with	O
the	O
Z80	B-General_Concept
(	O
signal	O
timing	O
,	O
pinout	O
&	O
function	O
of	O
pins	O
differ	O
from	O
the	O
Z80	B-General_Concept
)	O
.	O
</s>
<s>
Zilog	O
's	O
NMOS	B-Algorithm
Z800	B-Device
and	O
CMOS	B-Device
Z280	B-Device
were	O
16-bit	O
Z80	B-General_Concept
implementations	O
(	O
before	O
the	O
HD64180	B-General_Concept
/	O
Z180	B-Device
)	O
with	O
a	O
16MB-paged	O
MMU	O
address	B-General_Concept
space	I-General_Concept
;	O
they	O
added	O
many	O
orthogonalizations	O
and	O
addressing	B-Language
modes	I-Language
to	O
the	O
Z80	B-General_Concept
instruction	B-General_Concept
set	I-General_Concept
.	O
</s>
<s>
Minicomputer	B-Architecture
features	O
—	O
such	O
as	O
user	O
and	O
system	O
modes	O
,	O
multiprocessor	O
support	O
,	O
on	O
chip	O
MMU	O
,	O
on	O
chip	O
instruction	O
and	O
data	O
cache	O
,	O
and	O
so	O
on	O
—	O
were	O
seen	O
rather	O
as	O
more	O
complexity	O
than	O
as	O
functionality	O
and	O
support	O
for	O
the	O
(	O
usually	O
electronics-oriented	O
)	O
embedded	B-Architecture
systems	I-Architecture
designer	O
;	O
it	O
also	O
made	O
it	O
very	O
hard	O
to	O
predict	O
instruction	O
execution	O
times	O
.	O
</s>
<s>
Certain	O
arcade	O
games	O
such	O
as	O
Pang/Buster	O
Bros	O
use	O
an	O
encrypted	O
"	O
Kabuki	O
"	O
Z80	B-General_Concept
CPU	O
manufactured	O
by	O
VLSI	O
Technology	O
,	O
where	O
the	O
decryption	O
keys	O
are	O
stored	O
in	O
its	O
internal	O
battery-backed	O
memory	O
,	O
to	O
avoid	O
piracy	O
and	O
illegal	O
bootleg	O
games	O
.	O
</s>
<s>
During	O
the	O
late	O
1970s	O
and	O
early	O
1980s	O
,	O
the	O
Z80	B-General_Concept
was	O
used	O
in	O
a	O
great	O
number	O
of	O
fairly	O
anonymous	O
business-oriented	O
machines	O
with	O
the	O
CP/M	B-Application
operating	I-Application
system	I-Application
,	O
a	O
combination	O
that	O
dominated	O
the	O
market	O
at	O
the	O
time	O
.	O
</s>
<s>
Four	O
well-known	O
examples	O
of	O
Z80	B-General_Concept
business	O
computers	O
running	O
CP/M	B-Application
are	O
the	O
Heathkit	B-Device
H89	I-Device
,	O
the	O
portable	O
Osborne	B-Device
1	I-Device
,	O
the	O
Kaypro	O
series	O
,	O
and	O
the	O
Epson	B-Device
QX-10	I-Device
.	O
</s>
<s>
Some	O
systems	O
used	O
multi-tasking	O
operating	B-General_Concept
system	I-General_Concept
software	O
(	O
like	O
MP/M	B-Operating_System
or	O
Morrow	O
's	O
Micronix	O
)	O
to	O
share	O
the	O
one	O
processor	O
between	O
several	O
concurrent	B-License
users	I-License
.	O
</s>
<s>
Multiple	O
home	O
computers	O
were	O
introduced	O
that	O
used	O
the	O
Z80	B-General_Concept
as	I-General_Concept
the	O
main	O
processor	O
or	O
as	O
a	O
plug-in	O
option	O
to	O
allow	O
access	O
to	O
software	O
written	O
for	O
the	O
Z80	B-General_Concept
.	O
</s>
<s>
Notable	O
are	O
the	O
TRS-80	B-Device
series	O
,	O
including	O
the	O
original	O
model	O
(	O
later	O
retronymed	O
"	O
Model	O
I	O
"	O
)	O
,	O
Model	B-Device
II	I-Device
,	O
Model	O
III	O
,	O
and	O
Model	B-Device
4	I-Device
,	O
which	O
were	O
equipped	O
with	O
a	O
Z80	B-General_Concept
as	I-General_Concept
their	O
main	O
processor	O
,	O
and	O
some	O
(	O
but	O
not	O
all	O
)	O
other	O
TRS-80	B-Device
models	O
which	O
used	O
the	O
Z80	B-General_Concept
as	I-General_Concept
either	O
the	O
main	O
or	O
a	O
secondary	O
processor	O
.	O
</s>
<s>
Other	O
notable	O
machines	O
were	O
the	O
DEC	B-Device
Rainbow	I-Device
100	O
,	O
and	O
the	O
Seequa	B-Device
Chameleon	I-Device
,	O
both	O
of	O
which	O
featured	O
both	O
an	O
Intel	B-Device
8088	I-Device
and	O
a	O
Z80	B-General_Concept
CPU	O
,	O
to	O
support	O
either	O
8-bit	O
CP/M	B-Application
-80	I-Application
applications	O
running	O
on	O
the	O
Z80	B-General_Concept
,	O
or	O
a	O
custom	O
MS-DOS	O
that	O
was	O
not	O
fully	O
compatible	O
with	O
PC	B-Operating_System
DOS	I-Operating_System
applications	O
running	O
on	O
the	O
8088	B-Device
.	O
</s>
<s>
In	O
1981	O
,	O
Multitech	O
(	O
later	O
to	O
become	O
Acer	O
)	O
introduced	O
the	O
Microprofessor	B-Device
I	I-Device
,	O
a	O
simple	O
and	O
inexpensive	O
training	O
system	O
for	O
the	O
Z80	B-General_Concept
microprocessor	I-General_Concept
.	O
</s>
<s>
In	O
1984	O
Toshiba	O
introduced	O
the	O
Toshiba	O
MSX	B-Operating_System
HX-10	O
in	O
Japan	O
and	O
Australia	O
.	O
</s>
<s>
In	O
1985	O
,	O
Sharp	O
introduced	O
the	O
Hotbit	B-General_Concept
and	O
Gradiente	O
introduced	O
the	O
Expert	B-Device
,	O
which	O
became	O
the	O
dominant	O
8-bit	O
home	O
computers	O
in	O
Brazil	O
until	O
the	O
late	O
1980s	O
.	O
</s>
<s>
Use	O
of	O
the	O
Z80	B-General_Concept
in	O
lighter	O
,	O
battery-operated	O
devices	O
became	O
more	O
widespread	O
with	O
the	O
availability	O
of	O
CMOS	B-Device
versions	O
of	O
the	O
processor	O
.	O
</s>
<s>
It	O
also	O
inspired	O
the	O
development	O
of	O
other	O
CMOS	B-Device
based	O
processors	O
,	O
such	O
as	O
the	O
LH5801	O
from	O
Sharp	O
.	O
</s>
<s>
The	O
Sharp	B-Device
PC-1500	I-Device
,	O
a	O
BASIC-programmable	O
pocket	B-Device
computer	I-Device
was	O
released	O
in	O
1981	O
,	O
followed	O
by	O
the	O
improved	O
Sharp	B-Device
PC-1600	I-Device
in	O
1986	O
and	O
the	O
Sharp	B-Device
PC-E220	I-Device
in	O
1991	O
.	O
</s>
<s>
Later	O
models	O
of	O
the	O
Sharp	B-Application
Wizard	I-Application
series	O
of	O
personal	O
organizers	O
also	O
were	O
Z80	B-General_Concept
based	O
.	O
</s>
<s>
Laptops	B-Device
which	O
could	O
run	O
the	O
CP/M	B-Application
operating	I-Application
system	I-Application
just	O
like	O
the	O
desktop	O
machines	O
followed	O
with	O
Epson	B-Device
PX-8	I-Device
Geneva	I-Device
in	O
1984	O
,	O
and	O
in	O
1985	O
the	O
Epson	B-Device
PX-4	I-Device
and	O
Bondwell-2	B-Operating_System
.	O
</s>
<s>
While	O
the	O
laptop	B-Device
market	O
in	O
subsequent	O
years	O
moved	O
to	O
more	O
powerful	O
Intel	B-General_Concept
8086	I-General_Concept
processors	O
and	O
the	O
MS-DOS	O
operating	B-General_Concept
system	I-General_Concept
,	O
light-weight	O
Z80-based	O
systems	O
with	O
a	O
longer	O
battery	O
life	O
were	O
still	O
being	O
introduced	O
,	O
such	O
as	O
the	O
Cambridge	B-Device
Z88	I-Device
in	O
1988	O
and	O
the	O
Amstrad	B-Device
NC100	I-Device
in	O
1992	O
.	O
</s>
<s>
The	O
Z80-derived	O
Z8S180	B-Device
also	O
found	O
its	O
way	O
into	O
an	O
early	O
pen-operated	O
personal	B-Application
digital	I-Application
assistant	I-Application
,	O
the	O
Amstrad	O
PenPad	O
PDA600	O
in	O
1993	O
.	O
</s>
<s>
Hong	O
Kong-based	O
VTech	O
produced	O
a	O
line	O
of	O
small	O
laptop	B-Device
computers	I-Device
called	O
'	O
Lasers	O
 '	O
based	O
on	O
a	O
Z80	B-General_Concept
.	O
</s>
<s>
The	O
Cidco	B-Protocol
MailStation	I-Protocol
Mivo	O
100	O
,	O
first	O
released	O
in	O
1999	O
,	O
was	O
a	O
stand-alone	O
portable	O
email	O
device	O
,	O
with	O
a	O
Z80-based	O
microcontroller	B-Architecture
.	O
</s>
<s>
Texas	O
Instruments	O
produced	O
a	O
line	O
of	O
pocket	O
organizers	O
(	O
ending	O
in	O
2000	O
)	O
using	O
Toshiba	O
processors	O
built	O
around	O
a	O
Z80	B-General_Concept
core	O
;	O
the	O
first	O
of	O
these	O
was	O
the	O
TI	O
PS-6200	O
and	O
after	O
a	O
lengthy	O
production	O
run	O
of	O
some	O
dozen	O
models	O
culminated	O
in	O
their	O
PocketMate	O
series	O
.	O
</s>
<s>
The	O
Zilog	B-General_Concept
Z80	I-General_Concept
has	O
long	O
been	O
a	O
popular	O
microprocessor	B-Architecture
in	O
embedded	B-Architecture
systems	I-Architecture
and	O
microcontroller	B-Architecture
cores	O
,	O
where	O
it	O
remains	O
in	O
widespread	O
use	O
today	O
.	O
</s>
<s>
Applications	O
of	O
the	O
Z80	B-General_Concept
include	O
uses	O
in	O
consumer	O
electronics	O
,	O
industrial	O
products	O
,	O
and	O
electronic	O
musical	O
instruments	O
.	O
</s>
<s>
For	O
example	O
,	O
Z80	B-General_Concept
was	O
used	O
in	O
the	O
groundbreaking	O
music	O
synthesizer	O
Prophet-5	O
,	O
as	O
well	O
as	O
in	O
the	O
first	O
MIDI	O
synthesizer	O
Prophet	O
600	O
.	O
</s>
<s>
Casio	O
used	O
the	O
Z80A	B-General_Concept
in	O
its	O
PV-1000	B-Operating_System
video	O
game	O
console	O
.	O
</s>
<s>
A	O
good	O
number	O
of	O
early-1980s	O
arcade	O
video	O
games	O
,	O
including	O
the	O
arcade	O
game	O
Pac-Man	B-Application
,	O
contain	O
Z80	B-General_Concept
CPUs	B-General_Concept
.	O
</s>
<s>
The	O
Z80	B-General_Concept
was	O
used	O
in	O
the	O
Sega	O
Master	O
System	O
and	O
Sega	O
Game	O
Gear	O
consoles	O
.	O
</s>
<s>
The	O
Sega	B-Operating_System
Genesis	I-Operating_System
contains	O
a	O
Z80	B-General_Concept
,	O
with	O
its	O
own	O
8	O
KB	O
of	O
RAM	O
,	O
which	O
runs	O
in	O
parallel	O
with	O
the	O
MC68000	B-Device
main	O
CPU	O
,	O
has	O
direct	O
access	O
to	O
the	O
system	O
's	O
sound	O
chips	O
and	O
I/O	B-General_Concept
(	O
controller	O
)	O
ports	O
,	O
and	O
has	O
a	O
switched	O
data	O
path	O
to	O
the	O
main	O
memory	O
bus	O
of	O
the	O
68000	B-Device
(	O
providing	O
access	O
to	O
the	O
64	O
KB	O
main	O
RAM	O
,	O
the	O
software	O
cartridge	O
,	O
and	O
the	O
whole	O
video	O
chip	O
)	O
;	O
in	O
addition	O
to	O
providing	O
backward	B-General_Concept
compatibility	I-General_Concept
with	O
Master	O
System	O
games	O
,	O
the	O
Z80	B-General_Concept
is	O
often	O
used	O
to	O
control	O
and	O
play	O
back	O
audio	O
in	O
Genesis	O
software	O
.	O
</s>
<s>
Z80	B-General_Concept
CPUs	B-General_Concept
were	O
also	O
used	O
in	O
the	O
trailblazing	O
and	O
popular	O
TI-8x	B-Device
series	I-Device
of	I-Device
graphing	I-Device
calculators	I-Device
from	O
Texas	O
Instruments	O
,	O
beginning	O
in	O
1990	O
with	O
the	O
TI-81	B-Device
,	O
which	O
features	O
a	O
Z80	B-General_Concept
clocked	O
at	O
2MHz	O
.	O
</s>
<s>
Most	O
higher-line	O
calculators	O
in	O
the	O
series	O
,	O
starting	O
with	O
the	O
TI-82	B-Device
and	O
TI-85	B-Device
,	O
clock	O
their	O
Z80	B-General_Concept
CPUs	B-General_Concept
at	O
6MHz	O
or	O
higher	O
.	O
</s>
<s>
(	O
A	O
few	O
models	O
with	O
TI-8x	O
names	O
use	O
other	O
CPUs	B-General_Concept
,	O
such	O
as	O
the	O
M68000	B-Device
,	O
but	O
the	O
vast	O
majority	O
are	O
Z80-based	O
.	O
</s>
<s>
On	O
those	O
,	O
it	O
is	O
possible	O
to	O
run	O
assembled	O
or	O
compiled	O
user	O
programs	O
in	O
the	O
form	O
of	O
Z80	B-General_Concept
machine-language	O
code	O
.	O
)	O
</s>
<s>
The	O
TI-84	B-Device
Plus	I-Device
series	I-Device
,	O
introduced	O
in	O
2004	O
,	O
is	O
still	O
in	O
production	O
as	O
of	O
2020	O
.	O
</s>
<s>
The	O
TI-84	B-Device
Plus	I-Device
CE	O
series	O
,	O
introduced	O
in	O
2015	O
,	O
uses	O
the	O
Z80-derived	O
Zilog	B-Device
eZ80	I-Device
processor	O
and	O
is	O
also	O
still	O
in	O
production	O
as	O
of	O
2020	O
.	O
</s>
<s>
In	O
the	O
late	O
1980s	O
,	O
a	O
series	O
of	O
Soviet	O
landline	O
phones	O
called	O
"	O
AON	O
"	O
featured	O
the	O
Z80	B-General_Concept
;	O
these	O
phones	O
expanded	O
the	O
feature	O
set	O
of	O
the	O
landline	O
with	O
caller	O
ID	O
,	O
different	O
ringtones	O
based	O
on	O
the	O
caller	O
,	O
speed	O
dial	O
and	O
so	O
forth	B-Application
.	O
</s>
<s>
In	O
the	O
second	O
half	O
of	O
nineties	O
manufacturers	O
of	O
these	O
phones	O
switched	O
to	O
8051	O
compatible	O
MCUs	B-Architecture
to	O
reduce	O
power	O
consumption	O
and	O
prevent	O
compact	O
wall	O
power	O
adapters	O
from	O
overheating	O
.	O
</s>
