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> 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, the host shall make a transition to the HP2: Check_Status_B state.". The text doesnt state anything about BSY=1 and DRQ=1. There are other diagrams that have the case (BSY=1 & DRQ=0), and I think in all the device diagrams where BSY=1, you also have DRQ=0. So it seems to imply that whenever you have BSY=1 then DRQ=0, unless maybe you are looking at it while the device is transitioning. Anyway, assuming that the diagram/text really means: > BSY=0; DRQ=0 : HP2:HI0 > BSY=0; DRQ=1 : HP2:HP4 > BSY=1; DRQ=x : HP2:HP2 There's no case where you would do HP2:HP3... --Fabrice -----Original Message----- From: Pat LaVarre [mailto:[EMAIL PROTECTED] Sent: Wednesday, February 11, 2004 12:34 PM To: [EMAIL PROTECTED] Subject: Re: [t13] PACKET protocol. Host state diagram. > we have: > BSY=0; DRQ=0 : HP2:HI0 > BSY=0; DRQ=1 : HP2:HP4 > BSY=1; DRQ=0 : HP2:HP2 > BSY=1; DRQ=1 : ??? In a host's sample of x3F6 Alternate Status, or of x1F7 Status, seeing BSY=1 makes DRQ indeterminate. If the t13.org text tells the host to behave differently when DRQ=0 or DRQ=1 seen together with BSY=1, then the t13.org text errs. (Or else I've missed a significant backwards-incompatible change in the standard. I have not myself closely studied that text since I was last responsible for complying with it, which was Spring of 1998.) > "Host PACKET non-data and PIO data command state diagram" > (figure 53 in d1532v2r4.pdf). I'm ignoring the overlapped modes, > and I'm assuming nIEN=0. Delightfully precise cross-reference, thank you. Pat LaVarre bc: [EMAIL PROTECTED]
