The cable required to connect to a printer (or any other output device) is called a Null-modem cable (NMC). A technical explanation and drawing of the connections required is given in Appendix 1.
[[Image:RS232_illu_p7_1.jpg|400px]]
A Null-modem cable has Cable-sockets at each end to plug into the Chassis-plugs on the RS232C and the printer. If your printer has a Chassis-socket, then you will also require a converter cable comprising two back-to-back Cable-plugs.
[[Image:RS232_illu_p7_2.jpg|400px]]
== Spell 3: Setting the speed of your printer ==
== Spell 6: Redirecting printer output via the RS232C ==
[[Image:RS232_illu_p11.jpg|400px]]
Normally, printer output is sent to the parallel Centronics port at the rear of your computer. Having connected and set up the RS232C, the following commands will cause all printer output to be sent via the serial interface:
AMSTRAD BASIC: '''|SERIAL'''
CP/M 2.2: '''STAT LST:=TTY:'''
CP/M Plus: '''DEVICE LST:=SIO'''
When operating with CP/M, it is possible to program this re-direction as part of the loading process. For CP/M Plus, you should incorporate the command given above into the ‘'''PROFILE.SUB'''‘ file. For CP/M 2.2, you should use '''SETUP.COM''' as described in Appendix 2.
== Spell 7: Restoring printer output to the parallel port ==
[[Image:RS232_illu_p12.jpg|400px]]
Every time you reset the computer or move from BASIC to CP/M, or from CP/M to BASIC, the printer output will be restored to the parallel port. This can also be done using the commands:
AMSTRAD BASIC: |PARALLEL
CP/M 2.2: STAT LPT:=LPT:
CP/M Plus: DEVICE LST:=LPT
== Spell 8: Cables to connect Terminal Emulator to a minicomputer ==
[[Image:RS232_illu_p13.jpg|400px]]
In this manual, a commercial microcomputer that requires a terminal or Visual Display Unit (VDU) in order to operate is also referred to as a minicomputer.
It is possible to connect your computer fitted with RS232C as a substitute for a terminal attached directly to a minicomputer. The cable to use for this will depend on the minicomputer. Use either a Null-modem cable (Cable-socket to Cable-socket) if the minicomputer has a Chassis-plug, or a modern cable (Cable-socket to Cable-plug) if the minicomputer has a Chassis-socket. If in doubt, consult Appendix 1 and the hardware manual of the minicomputer.
== Spell 9: Attaching the Terminal Emulator to a minicomputer ==
[[Image:RS232_illu_p14.jpg|400px]]
The baud rate and framing parameters of the RS232C and minicomputer should agree, as discussed previously when attaching to printers.
The Terminal Emulator is entered by typing:
AMSTRAD BASIC: |TERMINAL
....and is exit-ed by [CTRL] [ESC]
Note that the Terminal Emulator ‘inherits‘ whatever keyboard values have been previously set up by BASIC, and also responds to the screen control codes described in the AMSTRAD computer‘s user instruction manual. It will often be convenient to set the [ESC] key to return a standard value by entering:
KEY DEF 66,0,27
== Spell 10: Terminal Emulator echo and control codes ==
[[Image:RS232_illu_p11.jpg|400px]]
The Standard Terminal Emulator sends all key-strokes to the minicomputer, displays all received printable characters, and obeys received control codes.
The minicomputer will normally echo the key-strokes sent to it, so that you can see (on the screen of the terminal) what you have typed, character by character. If the minicomputer does not perform such an echo, then it will be necessary for the Terminal Emulator to do it instead. This is achieved by typing:
|HALFDUPLEX
This local echo may be turned off by typing:
|FULLDUPLEX
For diagnostic purposes, it is sometimes convenient for the terminal to display control codes, rather than obey them. The Terminal Emulator can be switched between these two modes by the commands:
|CTRLDISPLAY …. And .... |CTRLACTION
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[[Category:Serial interfaces]]