andy pugh wrote: > On 26 January 2011 20:56, Igor Chudov <[email protected]> wrote: > >> The bad news is that the parallel port chipset that is on my new PC's >> motherboard, does not want to talk to PPMC when two encoder boards are >> installed in PPMC. >> > > Which motherboard? > > I assume that this is unrelated to the known problem with the Intel > D510MO which has been worked-around here? > http://git.linuxcnc.org/gitweb?p=emc2.git;a=commit;h=c9c7ebfa472dcd1de02ccb6470340a97f15a588e > > Yes, it appears unrelated. His PC motherboard works with ONE PPMC encoder board, but fails with TWO of them. It has to be some strange timing error. I have verified that two encoder boards work fine on the D510MO (after making some fixes to older encoder boards and DAC boards.) Every multi-IO chip has its own way of interpreting the incredibly lax specs of the IEEE-1284 protocol. Some boards put the data and WRITE/ signal out first, then provide the strobe pulse. Some put them out at the same time, one I saw actually put out the data and WRITE/ AFTER the strobe! Well, how much delay do you need to be sure the data and WRITE/ are stable? Who knows!! So, all this keeps me hopping whenever a new multi-IO chip comes out.
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