Appendix E: Use With Atari - Epson MX-70 User Manual

Appendix E
Use with Atari
Using Atari 800 Computer with Atari 850 Interface
Lines ending with a semicolon cause the Atari to automatically "pad" the rest
of the line with spaces until it is 40 characters long, when using LPRINT.
Therefore, it is advisable to avoid LPRINT. Fortunately, there is another
approach to printing that allows semicolons to be used without problems.
10 OPEN #7,8,0, "P"
#7 opens tile #7
8 signifies output device
0 is not used
P assigns device as printer
20 PRINT #7; "ABC";
30 PRINT #7; "DEF"
40 CLOSE #7
prints
ABCDEF
Port #7 is the printer port usually used by the Atari.
To use the ASCII control codes we often need to add 128. Atari uses codes O-31
for its graphics characters.
If inverse characters are sent as data in the "bit image" mode, the eighth bit will
be set, causing the top pin to fire for every character. Highly undesirable!
The Atari 8.50 interface has a 4 second time-out. If it does not receive an
acknowledge signal from the printer within 4 seconds of sending it a command,
the computer will send a "Device Nak," Error Code #139 message. The
program can catch this error using the BASIC "TRAP" command. Consult
your Atari manual for use of TRAP.
Semicolons or commas must be used to separate all literal and variable strings.
The maximum length of a string is 99 characters.
on printer.
APPENDIX E
89