[bug #7383] Hardware shortcut using KANDA STK200 compatible ISP cable

[avrs-admin]

Lore nobody@nongnu.org
Thu 22 Jan 2004 05:44:06 PM UTC

I'm using an KANDA STK200 compatible ISP cable (see attached file) with AVRDUDE 4.2.0
With this cable configuration, the 2 74HC244 buffer enable command are connectet tu 2 different DB25 pin. The goal of this wireing is to permit an hardware safe reset sequence, by activating only the chanel 2 buffer (pin 19) during Reset sequence.
Unfortunately I don't find in AVRDUDE how to separately command this 2 buffer and in the avrdude.conf file for the STK200 compatible cable "pony-stk200" the 2 buffer (pin 4 and 5) are activated at the same time.
I consider this realy dangerous (I already break some cips). It's possible de add a new connecting point to separately activate the 2 buffers ?
For information I actualy use the CodeVision integrated programmes. It correctly drive the 2 buffer but if posssible I will kome back to AVRDUDE.

Thank
Lore

file #1006: isp.gif

This issue was migrated from https://savannah.nongnu.org/bugs/?7383

[avrs-admin]

Joerg Wunsch <joerg_wunsch>
Sat 17 Sep 2005 07:26:24 PM UTC

The logic in par.c is set to immediately drive the /RESET
line as soon as the buffer's /CS is activated, so the window
where the buffer could potentially drive two active outputs
against each other is in the range of nanoseconds which
should be bearable (the worst effect is probably a spike in
the power supply).  Further, if you use MISO/MOSI for regular
IO that might conflict with ISP, it's always recommended to
have some small series resistors in these lines.

As the originator left no email address or other option to
get in contact with him, left no patch implementing a
suggested solution to the alleged problem, and rearranging
the code would be quite a bit of work, I'm closing this bug
as a "won't fix".