Re: Problem (toggle failure) with DS2408 -- fixed

OK, I was missing something important.

I didn't quite understand Cliff Brake's answer, but it made me double check the
datasheet for everything that has to do with reset functionality.

Turns out it was the following piece I have missed:
[RSTZ pin is a ...] SW configurable PIO reset input (/RST) or open-drain strobe
output (/STRB). When configured as /RST , a LOW input sets all PIO outputs to
the "off" state by setting all bits in the PIO Output Latch State Register. When
configured as /STRB , an output strobe will occur after a PIO write (see
Channel-Access Write command) or after a PIO Read (see Channel-Access Read
command). The power-on default function of this pin is /RST .

In the TINIs400 board this is intended to be used as a Strobe pin, so it is left
unconnected, somewhere near logic zero. With the default configuration of the
chip, this was seen as a continuous reset of the output latches. I pulled the
pin up and everything seems to be OK.

I'm just posting this to the list in case somebody else stumbles accross the
same problem while rushing to play with his new toy :) [exactly what happened to
me]

Thanks again,

Alexander Baxevanis

----- Original Message -----
From: "Cliff Brake" <cbrake.list-Bpo/[email protected]>
To: "Alexander Baxevanis" <[email protected]>; <[email protected]>
Sent: Thursday, January 22, 2004 9:06 PM
Subject: Re: [TINI]Problem (toggle failure) with DS2408


> On Thursday 22 January 2004 11:33 am, Alexander Baxevanis wrote:
> > Hello,
> >
> > I am using the TINIm400 module with the TINIs400 board (Rev B), which
> > includes the DS2408 chip for I/O.
>
> <snip>
>
> > The input logic levels are sampled properly (i.e. they show up as HIGH when
> > pulled up to Vcc) but toggling the switch fails for all switches.  I have
> > also tried to toggle the switches with custom code, but this also fails.
> > There is no Java exception being thrown and no other devices on the bus,
> > which pretty much rules out the possibility of communication failure.
> >
> > Do you think this is a hardware problem or am I missing something
> > important??
>
> Make sure the DS2408 power-on reset is cleared.
>
> Cliff
>
> ================
> FOM Systems
> http://fomsystems.com
>

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