* On Wed, Mar 25, 2020 at 04:26:19PM +0100 silverdr_at_wfmh.org.pl wrote: > > I can't even see how it would work. The 64 doesn't check for activity on the bus before driving it, so that would corrupt transfers in progress. > > My guess is that as long as ATN line is not used for data transfer (like in some ill-coded speeders that require disconnecting everything else off the bus in order to work) that might be enough to "signal" "I am not here for you" to the other computer. When ATN is asserted, the "ATN trap" interferes with a transmission that is currently in progress, because it sets the DATA line on all drives. So, if the other computer is bit banging when this happens, there will be an interference. However, if the "bus is open" (for example, there was a LISTEN or TALK), but there is currently no transmission, I am not sure if this could not work. IIRC, the floppy drive and the computer together will hold DATA and CLK low. Do I remember correctly? In this case, when Computer 2 asserts ATN, the ATN trap will pull DATA low. This is not a problem, as it is already low. However, there will be no transmission possible, so Computer 2 will eventually give an "device not present". Of course, this depends upon if my memory about CLK and DATA being set is true or not. Additionally, this would not work reliably, as it will not work if the ATN is set at a time when there is actually a bit banging happening. Regards, Spiro. -- Spiro R. Trikaliotis http://www.trikaliotis.net/Received on 2020-05-30 01:23:30
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