[Coco] parallel communications

James Dessart james at skwirl.ca
Mon Jun 21 13:08:19 EDT 2004

Would it be possible to use a 74374, with some address decoding logic, 
to make a 4-bit bi-directional parallel port? (of sorts) I want to make 
a programmer for SPI based microcontrollers, and the CoCo is the best 
candidate in my collection for the programming system.

Also, does anyone know what address 0x80 on a PC does? I think it's 
related to the parallel port, as the example code I'm looking at is 
writing to it. It's using the parallel port to do serial communications 
with a microcontroller for in-system programming. I'd like to make an 
interface card for the CoCo that'll let me program the microcontrollers 
from there.

Does anyone have any tips for this? I've got a spare 74374 lying 
around, along with other 7400 series TTLs, but not much experience in 
wiring them up. I'd like to keep from spending a cent on the 
programmer, and reuse as many chips I've got as possible. I guess the 
main thing would be the address decoding.. are there any tricks for 
fully decoding the 16-bit address while using the least possible chips?


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