From: Andre Fachat (
Date: 2004-07-10 12:57:07

On Tue, Jul 06, 2004 at 01:21:56PM +0200, Baltissen, GJPAA (Ruud) wrote:
> What really did please me was the fact that it also revealed that an active
> ATN negates NDAC and NRFD. So one thing I can do at least whenever I detect

If you look at the protocol, you see that active ATN negating NRFD and NDAC
automatically blocks the bus until the device (and that means all devices)
recognize the ATN, and set the signal to remove the block (un-negating the
NRFD/NDAC lines). If you look closer, you see that the block (negating NRFD/NDAC)
is done when the ATN line is different (XOR) from a special drive output
line (ATNA) that is used to acknowledge the ATN and unblock the bus after
change of ATN.


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