<s>
The	O
Commodore	O
serial	O
IEEE-488	O
bus	B-General_Concept
(	O
IEC	B-Protocol
Bus	I-Protocol
)	O
,	O
is	O
Commodore	O
's	O
interface	O
for	O
primarily	O
magnetic	B-General_Concept
disk	I-General_Concept
data	I-General_Concept
storage	I-General_Concept
and	O
printers	O
for	O
Commodore	O
8-bit	O
home	O
computers	O
:	O
the	O
VIC-20	B-Device
,	O
Commodore	O
64	O
,	O
Commodore	B-Device
128	I-Device
,	O
Plus/4	B-Operating_System
,	O
Commodore	B-Operating_System
16	I-Operating_System
,	O
and	O
Commodore	B-Device
65	I-Device
.	O
</s>
<s>
The	O
parallel	O
IEEE-488	O
interface	O
used	O
on	O
the	O
Commodore	B-Device
PET	I-Device
(	O
1977	O
)	O
computer	O
line	O
was	O
too	O
costly	O
,	O
so	O
a	O
cost	O
reduced	O
version	O
was	O
developed	O
,	O
which	O
consisted	O
of	O
a	O
stripped	O
down	O
,	O
serial	O
version	O
of	O
the	O
IEEE-488	O
interface	O
,	O
with	O
only	O
a	O
few	O
signals	O
remaining	O
;	O
however	O
,	O
the	O
general	O
protocol	O
layout	O
was	O
kept	O
.	O
</s>
<s>
Commodore	O
began	O
using	O
this	O
bus	B-General_Concept
with	O
the	O
VIC-20	B-Device
(	O
1980	O
)	O
.	O
</s>
<s>
Connection	O
to	O
the	O
computer	O
uses	O
a	O
DIN-6	B-Architecture
connector	I-Architecture
(	O
DIN	B-Architecture
45322	I-Architecture
)	O
.	O
</s>
<s>
The	O
bus	B-General_Concept
signals	O
are	O
digital	O
single-ended	O
open	O
collector	O
TTL	B-General_Concept
and	O
active	O
when	O
low	O
.	O
</s>
<s>
Bus	B-General_Concept
devices	O
have	O
to	O
provide	O
their	O
own	O
power	O
.	O
</s>
<s>
Because	O
the	O
bus	B-General_Concept
lines	O
are	O
electrically	O
open	O
collector	O
it	O
works	O
like	O
a	O
long	O
OR	O
gate	O
between	O
all	O
device	O
line	O
drivers	O
.	O
</s>
<s>
Transmission	O
begins	O
with	O
the	O
bus	B-General_Concept
talker	O
holding	O
the	O
Clock	O
line	O
true	O
,	O
and	O
the	O
listener(s )	O
holding	O
the	O
Data	O
line	O
true	O
.	O
</s>
<s>
When	O
all	O
bus	B-General_Concept
listeners	O
are	O
ready	O
to	O
receive	O
they	O
release	O
the	O
Data	O
line	O
to	O
false	O
.	O
</s>
<s>
The	O
Commodore	B-Device
1541	I-Device
floppy	O
drive	O
uses	O
a	O
slower	O
Commodore	O
64	O
compatible	O
mode	O
which	O
can	O
be	O
deactivated	O
for	O
faster	O
speed	O
by	O
using	O
the	O
command	O
OPEN	O
15	O
,	O
8	O
,	O
15	O
,	O
"	O
UI-	O
"	O
:CLOSE	O
15	O
.	O
</s>
<s>
+	O
Device	O
numbering	O
per	O
Commodore	O
64	O
KERNAL	B-Operating_System
ROM	O
Device	O
Type	O
0	O
Keyboard	O
1	O
Cassette	O
port	O
2	O
RS-232	O
on	O
the	O
user	O
port	O
or	O
second	O
cassette	O
on	O
PETs	O
3	O
Screen	O
4	O
–	O
5	O
Printer	O
6	O
Typically	O
plotter	O
device	O
7	O
Second	O
plotter	O
?	O
</s>
<s>
Device	O
number	O
0	O
–	O
3	O
are	O
not	O
associated	O
with	O
the	O
Commodore	B-Protocol
bus	I-Protocol
.	O
</s>
<s>
The	O
VIC-20	B-Device
computer	O
and	O
the	O
Commodore	B-Device
1540	I-Device
and	O
1541	B-Device
floppy	O
drives	O
use	O
the	O
MOS	B-Device
Technology	I-Device
6522	I-Device
VIA	O
to	O
handle	O
IEC	B-Protocol
Bus	I-Protocol
transmissions	O
.	O
</s>
<s>
The	O
Commodore	O
64	O
and	O
128	B-Device
computers	O
and	O
the	O
Commodore	B-Device
1571	I-Device
drive	O
use	O
the	O
Complex	B-Device
Interface	I-Device
Adapter	I-Device
.	O
</s>
