Oki OKIPAGE 10ex Troubleshooting Manual page 33

(1) RS-232C Interface
The serial data RXD from the host system, whose line voltage is clamped at the TTL level
by D4/D512, are received by the CPU built-in serial controller.
DSR and CTS signals are terminated through 5.6k resistors. Send signals TXD, RTS and
DTR are put out from the CPU and are sent to lines through a line driver IC (75188).
101
CPU
108
102
103
(a) Send signal level
Input 0V
Output 0V
40990901TH Rev.1
Option
connector
RSRXDO-N
RSTXDO-P
RSRTDO-N
RSDTDO-N
TTL level
+8V
-8V
+5V
3.3K
5.6K
5.6K
5.6K
75188
Idle
+8V -8V
(b) Receive signal level
Input 0V
Output 0V
SERIAL
RXD
2
DSR
6
CTS
8
CD
1
TXD
3
RTS
7
DTR
4
SSD
9
+8V
-8V
TTL level
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