Appendix B - Serial port and transfer protocols

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-   -  
2TxD -> 3RxD 
3RxD <- 2TxD 
4RTS -> 5CTS 
5CTS   20DTR 
6-   -  
7GND   7GND 
8DCD   20DTR 
9DTR   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

SequenceFunction
ESC NStart of file name
ESC FStart of file/end of file name
ESC EEnd of file
ESC ZEnd of file or end of list of files
ESC B x xWhere 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.