<s>
The	O
Zilog	B-Device
Z280	I-Device
is	O
a	O
16-bit	B-Device
microprocessor	B-Architecture
,	O
an	O
enhancement	O
of	O
the	O
Zilog	B-General_Concept
Z80	I-General_Concept
architecture	O
,	O
introduced	O
in	O
July	O
1987	O
.	O
</s>
<s>
It	O
is	O
basically	O
the	O
Z800	B-Device
,	O
renamed	O
,	O
with	O
slight	O
improvements	O
such	O
as	O
being	O
fabricated	O
in	O
CMOS	B-Device
.	O
</s>
<s>
Zilog	O
added	O
a	O
memory	B-General_Concept
management	I-General_Concept
unit	I-General_Concept
(	O
MMU	O
)	O
to	O
expand	O
the	O
addressing	B-General_Concept
range	I-General_Concept
to	O
16MB	O
,	O
features	O
for	O
multitasking	B-Operating_System
and	O
multiprocessor	B-Operating_System
and	O
coprocessor	B-General_Concept
configurations	O
,	O
and	O
256	O
bytes	O
of	O
on-chip	O
static	O
RAM	O
,	O
configurable	O
as	O
either	O
a	O
cache	B-General_Concept
for	O
instructions	O
and/or	O
data	O
,	O
or	O
as	O
part	O
of	O
the	O
ordinary	O
address	B-General_Concept
space	I-General_Concept
.	O
</s>
<s>
It	O
has	O
a	O
huge	O
number	O
of	O
new	O
instructions	O
and	O
addressing	B-Language
modes	I-Language
giving	O
a	O
total	O
of	O
over	O
2000	O
combinations	O
.	O
</s>
<s>
It	O
offers	O
Supervisor	O
and	O
User	O
operating	O
modes	O
,	O
and	O
optionally	O
separate	O
address	B-General_Concept
spaces	I-General_Concept
for	O
instructions	O
and	O
data	O
in	O
both	O
modes	O
(	O
four	O
total	O
possible	O
address	B-General_Concept
spaces	I-General_Concept
)	O
.	O
</s>
<s>
a	O
12MHz	O
CPU	B-Device
with	O
a	O
3MHz	O
bus	B-General_Concept
)	O
.	O
</s>
<s>
Unlike	O
the	O
Z80	B-General_Concept
the	O
Z280	B-Device
uses	O
a	O
multiplexed	O
arrangement	O
for	O
its	O
address	O
and	O
data	O
busses	O
.	O
</s>
<s>
More	O
successful	O
extensions	O
of	O
the	O
Z80-architecture	O
include	O
the	O
Hitachi	B-General_Concept
HD64180	I-General_Concept
in	O
1986	O
and	O
Zilog	B-Device
eZ80	I-Device
in	O
2001	O
,	O
among	O
others	O
.	O
</s>
<s>
See	O
further	O
Zilog	B-Device
Z800	I-Device
.	O
</s>
<s>
The	O
Z280	B-Device
had	O
many	O
advanced	O
features	O
for	O
its	O
time	O
,	O
most	O
of	O
them	O
never	O
seen	O
again	O
on	O
a	O
Zilog	O
processor	O
:	O
</s>
<s>
Multiple	O
I/O	O
pages	O
,	O
which	O
also	O
allows	O
for	O
internal	O
I/O	O
devices	O
without	O
restricting	O
the	O
address	B-General_Concept
range	I-General_Concept
of	O
the	O
I/O	O
ports	O
like	O
on	O
eZ80	B-Device
,	O
or	O
conflicting	O
with	O
existing	O
motherboard	B-Device
devices	O
,	O
like	O
the	O
Z180	B-Device
.	O
</s>
