14 Apr
2017
14 Apr
'17
6:16 p.m.
On 15/04/2017, at 1:45 AM, Fred Cisin via cctalk <cctalk at classiccmp.org> wrote:
I had thought that both ends of the Screen printer
cable would be 40 pin, That's why I had speculated on Model 3.
But I never spent $599 for one.
(instead, I struggled with interfacing a DTC-300 HyType 1 serial printer)
I never had a Screen Printer either, but I don't think it would even be possible to
use with a Model III.
I assumed the way it worked on the Model I was by either watching the CPU bus and sniffing
writes to the video memory (mirroring to its own copy continuously), or reading the video
memory when needed (trickier with synchronisation).
Unfortunately, despite the Model III having 50 pins instead of 40, 25 of them were ground
and A0-A7 of the address lines were exposed. Even that was only enabled for IO ports via
software first. The Model I was much for flexible for add-ons.
Scott.