EP405 GPIO signal problem

Toni Van Remortel t.vanremortel at ha.be
Fri Nov 21 19:21:46 EST 2003

Op do 20-11-2003, om 19:19 schreef Eugene Surovegin:
> On Thu, Nov 20, 2003 at 03:02:15PM +0100, Toni Van Remortel wrote:
> > 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)
> One thing which looks strange to me. Are you sure you can use 32 GPIO
> pins?

Ain't possible, I know.

> This is impossible because 405GP has only 23, and I doubt you can use
> even this number, because some of the pins are shared with IRQ and
> PerCSx lines.

You can set all 23 GPIO's as output. I actually only use 17 of them (2 x
8bit position and 1 on/off).
Now I've taken a deeper look at the problem, it might be caused by the
EP405 itself. My DAC settles at 70ns.
I still have to check if the signals are outputted all at the same time.
Should go and fetch a logic analyzer somewhere ;)

                           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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