RE: IEEE protocol under BASIC V4

From: Baltissen, R (Ruud) (
Date: 2003-05-28 08:41:28

Hallo Greg,

> Your "ReadIEEE" should change nRFD before it reads the data; it
> should change nDAC after it reads the data.

You are absolutely right. 

>      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.)

Thanks for all the comments. I understand the behaviour of both devices
except this particular piece. What I did in the first place was looking for
ATN = (L) after sending $04. Nothing found :( In fact an ATN = (L) is
detected after '$01 $04 $01 $01'. FYI, I didn't change the original send
routine, I only checked ATN between every transmission. But to make things
even weirder: I decided to drop this problem for the moment and to remove
all changes I made to trap ATN. But instead of typing 'load"$",8', I typed
'directory' out of habbit. Small suprise, data appeared on the sreen !!! You
should know that when I tried to intercept the data sent by the 8032,
nothing appeared at all. 
Unfortunately the data was scambled, that is, a number of random numbered
BASIC-lines with garbage. Repeating 'directory' several times showed me a
different output every time with one exception: the very first number was
always the same. One more info: the line numbers were made of actual data.

The only thing I can think of is placing $01 on the bus, pulling DAV (L) and
see what happens.

Hmmmm, these 'spurious signals' ie. all handshake lines (H), that is weird
as well. Have a look yourself: during normal transmissions whatever happens,
at least either NDAC or NRFD is (L) and in between both are (L). Except at
this particular point. Could this mean someting ??? I already said, normally
the sender waits for NDAC = (L) and NRFD = (H), source: 'PET revealed' and
other docs. And yet someone, I suspect the drive, pulls DAV (L).

Any comment is welcome. At least I have again some strings to clamp on :) 

   / __|__
  / /  |_/     Groetjes, Ruud
  \ \__|_\



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