[En-Nut-Discussion] SPI Bus

[Bernd Walter]

On Sat, Feb 21, 2009 at 12:49:25AM -0300, Thiago A. Corrêa wrote:
> Hi,
> 
>    I'm now porting the SPI Bus, and as always, I'm taking the at91 as
> example. Is there any reason why the at91 driver is not using the PCS
> to let the chip auto manage the CSn line?

The automangement often doesn't match with the slaves expectations.
Some slaves require the CS to be asserted over a complete sequence,
while the SPI controller deasserts it very quick.
And sometimes people want more than 4 slaves.
I assume almost everyone is doing it manually.

>    Is the shadowing of the MR intentional? or just a consequence of
> the CSR? I mean, can we have on the same bus peripherals with MODFDIS
> and without?
> 
>    I would appreciate some clarification on those. Thanks :)

-- 
B.Walter <bernd at bwct.de> http://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.