Appendix B - Serial port and transfer protocols
- Gunther Strube
- Vic Gerhardi
Z88 to Serial Printer Connections
This section 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.
WARNING
DO NOT USE THIS CABLE TO CONNECT TO A COMPUTER. IT WILL NOT WORK.
Import/Export Protocol
The Imp-Export protocol for Send & Batch Send/Receive functions is given here for programmers who want to interface the Cambridge Z88 to a computer by writing their own interface software.
Control sequences
| Sequence | Function |
|---|---|
| ESC N | Start of file name |
| ESC F | Start of file/end of file name |
| ESC E | End of file |
| ESC Z | End of file or end of list of files |
| ESC B x x | Where x x is two ASCII digits representing a hex byte. For example, the byte &A9 is transmitted with ESC B A 9. |
Note that all the characters after the ESC code must be in upper-case ASCII.
Transfer protocol
First file, and subsequent files:
ESC N filename ESC F data ESC E
Last file:
ESC N filename ESC F data ESC Z
where data is a sequence of characters in the range &20 to &7E. Codes in the range &00 to &1F and &7F to &FF should be transmitted using the ESC B prefix. The ESC B sequence is not accepted as part of the filename.
Import/Export will give a Suspended message 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.
The filename can be omitted.
XMODEM/YMODEM Protocol
This may be found on the internet. See XMODEM/YMODEM PROTOCOL
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.