piclist 2003\11\10\005644a >
Thread: SX Stack Problems
face BY : Josh Koffman email (remove spam text)

Just in case anyone on here isn't on the Ubicom portal or Yahoo Group.
Sorry if you're sick of seeing this post!

Hi all. Appologies to those who will be seeing this twice, I will be
posting it on theUbicom portal as well.

I am trying to get the SX Ethernet TCP/IP stack running, and I am
having no luck. I have the following sequence:
                                ; strobe IOWB pin
                                 jmp     $+1
                                 clrb    IOWB_PIN
                                 jmp     $+1
                                 jnb     IOCH_PIN, $
                                 setb    IOWB_PIN

The pins are defined elsewhere. My problem is that I never see
IOCH_PIN drop (using my scope) which it should to aknowledge the
data write. I don't know why this is happening. My initial thought is
that the SX isn't giving the 8019AS enough time to read before
bringing the line back up again. The idea is that the SX puts data on
the bus, then drops the IOWB pin. It should then wait for the
8019AS to drop the IOCHRDY line, then raise it again to acknowledge
the read. The SX is running at 50MHz. However, this line
puzzles me:
                                 jnb     IOCH_PIN, $
IOCH_PIN has a pullup resistor on it. The way I read this is that if
IOCH_PIN is low, jump to the same line. Therefore it's a loop to wait
for  IOCH_PIN to go high. but since it's already high, the code
always seems to cruise right through this. Is the code counting on
the "jmp     $+1" line to give the 8019AS enough time to drop the
line? Then the SX would want to wait for it to go high again,
as in the jnb line above?

Does this even make sense? Any help would be appreciated.


                 Josh Koffman
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completely foolproof is to underestimate the ingenuity of complete
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