From: Greg King (gngking_at_erols.com)
Date: 2003-05-28 07:10:10
-----Original Message-----
From: Baltissen, R (Ruud)
Date: Monday, May 26, 2003, 09:34 AM
> Who negates DAV?
> What triggers the computer to drive ATN (L)?
> My "ReadIEEE" reads the data on the bus when DAV goes (L),
> and after pulling nDAC and nRFD (L).
> My sniffer, which records every change, sees this:
Your sniffer's data, and other documents
that I've read, show the following things:
The talker controls EOI and DAV. The listenner controls nDAC and nRFD.
The computer controls ATN. It uses ATN to force all devices to listen to it.
It needs to do that when it sends device-numbers, device-commands
(OPEN, CLOSE, TALK, LISTEN, UNTALK, and UNLISTEN), channel-numbers,
and file-names. nRFD and nDAC are active high, the other signal lines are
active low. Your "ReadIEEE" should change nRFD before it reads the data; it
should change nDAC after it reads the data.
I added a description of the conversation between the computer
and the disk-drive. It explains the timing of the signals.
00 0 1 0 1 1
60 0 1 0 1 1 <- comp.: grabs the data-bus. (V4's 7th byte)
60 0 1 0 0 1 <- comp.: "Here is data."
Data ATN nRFD nDAC DAV EOI
60 0 0 0 0 1 <- drive: "OK, I'll look at it."
60 0 0 1 0 1 <- drive: "OK, I saw it."
60 0 0 1 1 1 <- comp.: "OK, I know that you saw it."
00 0 0 1 1 1 <- comp.: releases the bus.
00 0 0 0 1 1 <- drive: "OK, I saw your OK."
00 1 0 0 1 1 <- comp.: "All units can stop listenning."
00 1 1 0 1 1 <- comp.: "I'm ready to see a byte."
01 1 1 0 1 1 <- drive: grabs the data-bus.
01 1 1 0 0 1 <- drive: "Here is data."
01 1 0 0 0 1 <- comp.: "OK, I'll look at it."
01 1 0 1 0 1 <- comp.: "OK, I saw it."
00 1 0 1 0 1 <- drive: releases the bus.
00 1 0 1 1 1 <- drive: "OK, I know that you saw it."
00 1 0 0 1 1 <- comp.: "OK, I saw your OK."
00 1 1 0 1 1 <- comp.: "I'm ready to see the next byte."
04 1 1 0 1 1 <- drive: grabs the data-bus.
04 1 1 0 0 1 <- drive: "Here is data."
04 1 0 0 0 1 <- comp.: "OK, I'll look at it."
04 1 0 1 0 1 <- comp.: "OK, I saw it."
00 1 0 1 0 1 <- drive: releases the bus.
Data ATN nRFD nDAC DAV EOI
00 1 0 1 1 1 <- drive: "OK, I know that you saw it."
00 1 0 0 1 1 <- comp.: "OK, I saw your OK."
00 1 1 0 1 1 <- comp.: "I'm ready to see the next byte."
00 1 1 1 1 1 <- (I suspect that these are spurious
01 1 1 1 1 1 signals. The computer is changing its
01 1 1 1 0 1 direction; but, it's fighting with
00 0 0 0 0 1 the drive which still is talking!)
48 0 0 0 0 1
48 0 0 0 1 1 <- (The signals are back to normal.)
48 0 1 0 1 1 <- drive: "I'm ready to see a byte."
48 0 1 0 0 1 <- comp.: "Here is data."
48 0 0 0 0 1 <- drive: "OK, I'll look at it."
48 0 0 1 0 1 <- drive: "OK, I saw it."
48 0 0 1 1 1 <- comp.: "OK, I know that you saw it."
00 0 0 1 1 1 <- comp.: releases the bus.
00 0 1 0 1 1 <- drive: "OK, I saw your OK."
60 0 1 0 1 1 <- (This conversation is repeating itself.
60 0 1 0 0 1 Start at the top, and read down.)
60 0 0 0 0 1
60 0 0 1 0 1
Data ATN nRFD nDAC DAV EOI
60 0 0 1 1 1
00 0 0 1 1 1
00 0 0 0 1 1
00 1 0 0 1 1
00 1 1 0 1 1
01 1 1 0 1 1
01 1 1 0 0 1
01 1 0 0 0 1
01 1 0 1 0 1
00 1 0 1 0 1
00 1 0 1 1 1
00 1 0 0 1 1
00 1 1 0 1 1
01 1 1 0 1 1
01 1 1 0 0 1
01 1 0 0 0 1
01 1 0 1 0 1
00 1 0 1 0 1
00 1 0 1 1 1
00 1 0 0 1 1
Data ATN nRFD nDAC DAV EOI
00 1 1 0 1 1
00 1 1 1 1 1 <- (Spurious signals, again.)
00 1 1 1 0 1
00 0 0 0 0 1
48 0 0 0 1 1 <- (These are normal.)
48 0 1 0 1 1 <- drive: "I'm ready to see a byte."
48 0 1 0 0 1 <- (You know the rest of this conversation.)
48 0 0 0 0 1
48 0 0 1 0 1
48 0 0 1 1 1
00 0 0 1 1 1
00 0 1 0 1 1
60 0 1 0 1 1
60 0 1 0 0 1
60 0 0 0 0 1
60 0 0 1 0 1
60 0 0 1 1 1
00 0 0 1 1 1
00 0 0 0 1 1
00 1 0 0 1 1
Data ATN nRFD nDAC DAV EOI
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