APPENDIX D
Appendix D
TRS-80 Differences
This MX-70 Manual is designed around the Apple II for reasons discussed in Chapter 2. Fortunately, TRS-80 users can use it successfully by following the notes and suggestions in this appendix and throughout the text. In fact, using the MX-70 with the TRS-80 is quite easy: with no ports to initialize, no control codes needed to permit 80 column listings, and straightforward LPRINT com- mands.
General Changes
All TRS-80 models use LPRINT and LLIST to send information to the printer.
Be sure to change all PRINTS intended for the printer to LPRINT.
Ignore all references to PR#l and PR#O. They are for the Apple, as noted.
It may be necessary (and is usually permissable) to add 128 to certain code numbers, (but not when in graphics mode). For example, if CHR$(27) “A” CHR$ (12) doesn’t work, use CHR$(27) “A” CHR$(140). The problem is with the computer.
TRS-80 Model I Without Expansion Interface
Model I TRS-80 owners may use Radio Shack printer interface #26-1411 in place of the Radio Shack expansion interface, if necessary.
TRS-80 Model I With Expansion Interface
Graphics Codes
Sending graphics codes to the MX-70 via Model I BASIC has its drawbacks. Entering graphics mode can be an adventure if we try, for example, to specify a line length of 10. BASIC intercepts this code, and passes it down the line as a 13. So the printer expects 13 columns though we sent it only 10.
Once in graphics mode, certain codes must be sent via POKE rather than LPRINT CHR$. The Model I printer driver interprets CHR$(O) as a null code and does not pass it on to the printer. That hurts since we need this code in graphics mode.