Product: CAI/O Board and 40-column
Printer Model CAI/P40
From: CAI Instruments, 2559
Arbutus Ct., Midland, MI
48640, 517/835-6145.
Price: CAI/O board $79.95 alone,
$69.95 with any CAI peri-
pheral. Printer $119.95.
CAI Instruments has produced and documented an easy-to-use, relatively inexpensive printer and interface for 8K ZX computers. If you held off buying CAI’s Widget, you’ll find the CAI/O-printer combination worth the wait.
As CAI’s redesigned Widget, the CAI/O board has serial and parallel I/O ports plus CAI’s printer interface and tape controller. We only tested the board as it works with the printer. As a side note, the Widget has been streamlined internally to 7 chips and 3 EPROM sockets on a single board.
By ZX standards the printer is fairly large, about 10x7x2″. Hook-up could not have been easier. The CAI/O board, needed to run the printer, plugs onto the rear edge connector of the computer. Another connector accepts RAM. The printer plugs into the wall for power and into the CAI/O board via ribbon cable. The simple directions require no technical knowledge.
I had only two small problems: After a few hour’s operation, the printer skipped characters in the middle of the paper. Also, my computer crashed with a program loaded but not running crashed after 2 hours. CAI replaced I/O board and printer quickly and the second units have worked perfectly for over a week.
ZX81 keyboard printer commands don’t work with CAI’s printer. You use USR calls to routines in the printer’s internal software. For example, to print out a program in memory, type LET Z=USR 8195. Not as convenient as LLIST, but just as effective. Six USR calls operate the printer in one of 3 modes: print with variable (like LPRINT), list program in memory (like LLIST) and screen dump (like COPY). Each of these 3 can be printed in either regular or enhanced mode, which is twice normal height. Check page 17 for an example of enhanced mode.
To print, the computer must be in FAST. Internal software creates 3 error codes not used by Sinclair to catch errors, so you won’t crash the computer by making a mistake.
You get 40 print columns, which is wider than the ZX80/81’s screen display. CAI sells the 4.2″ thermal paper at $1.95/roll (but any thermal paper that size works).
Unlike the Widget, this board and printer don’t eat up RAM. They work with 16 & 64K RAMs (the 16K pack needs no changes; for 64K cut out the 8-16K block–DIP switches set to 1-OFF 2-OFF 3-OFF 4-ON).
What I like about CAI’s printer: It operates quietly (unlike Sinclair’s). It can print in large characters. It is available now. And the documentation is easy to follow and provides simple tests of all functions.
What I don’t like: Not being able to use the keyboard printer commands is moderately inconvenient at first, although I quickly memorized the most-used USR calls. Because of the layout of the CAI/O board’s edge connectors, attaching these units to 8K ZX80s is unwieldy. The design makes it tough to plug in the power jack. And the 40-column output means you won’t get a program listing in screen format, which I find useful for proofreading. Also, the printer puts an extra space after some keywords like LET (see examples on pp. 9 & 17), again messing up the screen format.
But overall, these objections are minor compared to the benefits of these two units. I was very pleased with the performance of my CAI/O board and printer.