This message is from the T13 list server.
> > In a host's sample of x3F6 Alternate Status, or of x1F7 Status, seeing > > BSY=1 makes DRQ indeterminate. > > Make sense... Actually the diagram shows only BSY=1 for the HP2:HP2 > transition. The text however, states "When BSY is set to one, and DRQ is > cleared to zero, Ugh. This English is wrong. When BSY is set to one, DRQ is unknowable. However, I agree we probably want the host to behave as if DRQ == 0 whenever BSY == 1. I know myself I have often written code like: xx = i(0x3F6); if ((xx & 0x80) != 0) xx &= 0x80; Supposedly unnecessary code like this spends code space and run time to force these indeterminate bits to appear determinate, so that by construction the people writing the code of the layer above cannot make the error of branching on these indeterminate bits. Pat LaVarre
