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CPU recognizes the optional interface connected to each port
through status read, and I/O memory area is allocated for
individual interfaces via port select.
Option port
OPT 2
OPT3
OPT4
Optional port
0PT2
0PT3
0PT4
1.2.9
RS232C (option)
RS232C
serial interface connected to I/O MOTHER.
1.2.10 CENTRONICS (Option)
CENTRONICS interface connected to I/O MOTHER.
1.2.11 COMMUNICATION (Option)
COMMUNICATION interface connected to I/O MOTHER
1.2.12 CURRENT LOOP (Option)
CURRENT LOOP interface connected to I/O MOTHER.
Table 1.2.2
Port select
8
6
A
A7 A
A5 A4 A3 A2 A1 AO A
1 0 0
0
Addre8s
• L u
u within port
1 0
0
1
1 0
1 0
.
Note:
Option interface
RS232C
RS232C
RS232C
8
A7 A
1 0
1 1 0
"
1 1 0
"
8
AO ' v A
are address buses.
CENTRONICS CURRENT LOOP
COMMUNICATION CURRENT LOOP
H.DISK I/F CURRENT LOOP
1-15
Status read
6
A5 A4 A3 A3 Al A0
1 1
-
0
_
1
-
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