Appendix B - Serial port
- Gunther Strube
- Vic Gerhardi
This appendix describes the pin connections for the Cambridge Z88 serial connector.
The following connections are for a cable to connect the Cambridge Z88 serial port connector to a 25-pin D-type serial printer connector, or equivalent:
| Cambridge Z88 9 way D (Male) | Printer - 25 way D (Male) | ||||||
|---|---|---|---|---|---|---|---|
| 1 | - | - | |||||
| 2 | TxD | -> | 3 | RxD | |||
| 3 | RxD | <- | 2 | TxD | |||
| 4 | RTS | -> | 5 | CTS | |||
| 5 | CTS | 20 | DTR | ||||
| 6 | - | - | |||||
| 7 | GND | 7 | GND | ||||
| 8 | DCD | 20 | DTR | ||||
| 9 | DTR | 6,8 | (DSR,DCD) | ||||
where the signals are as follows:
TxD Transmitted data
RxD Received data
RTS Request to send
CTS Clear to send
GND Signal ground
DCD Data carrier detect
DTR Data terminal ready
Notes
The Cambridge Z88 RS232 port is wired as Data Terminal Equipment
Pin 1 must not be used for RS232 signals. It carries +5v at 10pA, even when the machine is OFF.
Do not use pin 6 on the Cambridge Z88 connector.
Pin 9 is the RS232 DTR signal. It provides +5v at 1mA while the Cambridge Z88 is switched on,for powering CMOS serial to parallel converters.
CTS on the Cambridge Z88 must be high for the Cambridge Z88 to transmit, and DCD must be high for the Cambridge Z88 to receive. For simple RS232 use, connect pins 5 and 8 to pin 9, and connect pins 2 (TxD), 3 (RxD), and 7 (GND) to the other computer.
A Suspended message will be displayed if a battery low is flagged while sending or receiving, or if the Cambridge Z88 is switched off or the flap is opened. In this case you must repeat the transfer.