EP405 GPIO signal problem

Toni Van Remortel t.vanremortel at ha.be
Fri Nov 21 01:02:15 EST 2003


I have an RTAI powered kernel module which outputs 32 bits data via the
EP405 GPIO ports from the IBM 405GP CPU. These outputs are multiplexed
with other signals.
Problem: when I output the 32 bits as one like this:
writel( buffer, (u32)gpio_base_addr+GPIO0_OR );
(where buffer is of u32 type)
I get some glitches after my DAC. The DAC has a 70ns settling time, but
the glitches are 120µs. So I presume it's a CPU problem.

Is this a normal thing? I don't think so. It is strange behavior, that's
all I know. How can I prevent those 'peaks' in my output? Peaks are
generated by 0xFFFFFFFF output (that's what I can make out of the
                           Toni Van Remortel
              Wetenschappelijk Medewerker - D-science lab
  Real time Linux for embedded systems: http://linemb.d-sciencelab.com
              Tel: +32 3 205 61 72 - Fax: +32 3 205 61 95
                      E-mail: t.vanremortel at ha.be

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