From: Jim Brain (brain_at_jbrain.com)
Date: 2004-10-21 05:44:56
Spiro Trikaliotis wrote: >Anyway, as JD seems to be quite synchronous - which is not good for a >multitasking, non-RT OS - I doubt it will be possible to have good >support for it. I hoped JD to be truly asynchronous. > > I think your terms are backwards (JiffyDOS is very timing dependent, like RS232, which is called asynchronous operation, but I know what you are saying. It might be possible, as JDos syncs with data at the start of each byte, as I recall, but then the byte comes in 4 half nybble (twobits?) chunks of 13-14uS intervals. on the trace I have: time 0 data goes high to signal new byte. (not sure which side does this. I think receiving side) time 7 first 2 bits time 20 next 2 time 34 next 2 time 47 last 2 time 54 release data line to high time 62 other side acks by bringing low. If you can kills IRQs for 60uS or so, you might be able to do it, as long as the code you have can hit each of the twobit times within 7uS (sample at midpoints: 14,28,42,49 uS +- 3 uS or so) -- Jim Brain, Brain Innovations email@example.com http://www.jbrain.com Dabbling in WWW, Embedded Systems, Old CBM computers, and Good Times! Message was sent through the cbm-hackers mailing list
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