Casio I/O-PB-11 Service Manual page 13

2. On line circuit (RS-232C)
The on line port (RS-232C) is controlled by the USART µPD71051 and
supported only asynchronous communication.
RDTM
IC8
D4
12 8
1
DSR
IC8
D6
9 11
19
CTS
RXD
DTR
RTS
TXD
Pin description of UPD71051C
Pin No. Signal
1,2,5~8, D0~D7
27,28
3 RxDATA
9 TxCLK
10 WR
11 CS
12 C/D
13 RD
14 RxRDY
15 TxRDY
16 SYNC/BRK
17 CTS
18 TxEMP
19 TxDATA
20 CLK
21 RESET
22 DSR
23 RTS
24 DTR
25 RxCLK
26 VDD
V-
C14
2
RA2
3 1
IC3
C16
2
3 1
IC6
C15
5
6 4
IC6
C18
9
8 10
IC6
C17
12
11 13
IC6
GND
Description
Data bus
Receive data input
Transmitter clock input
Write signal
Chip select signal Input
Control or data change
Read signal
Receive ready output
Transmittor ready output
Syncronization/Break (Not used)
Clear to send signal input
Transmitter empty
Transmit data output
Clock input
Reset input
Data set ready signal input
Request to send signal output
Data terminal ready signal output
Receiver clock input
VCC(+5V) terminal
— 11 —
R21
GND
GND
V+
14
Vcc
2
4
5
9
10
12
13
C12
Pin description of on line connector
Pin No. Signal
1 SG
2 NC
3 ER
4 SD
5 RTS
6 NC
7 RD
8 CTS
9 CD
10 DR
11 NC
12 NC
13 CI
GND
13
12
11
10
9
8
7
6
V-
5
1
4
3
3
2
1
6
GND
8
11
C13
7
GND
Description
Signal ground
Non connection
Equipment ready
Send data
Request to send
Non connection
Receive data
Crear to send
Carrier detect
Data ready
No connection
No connection
Calling indicator
CI
NC
NC
DSR
CD
CTS
RXD
NC
RTS
TXD
DTR
NC
GND