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FW: do Ineed to use a timer if using the SPI as a slave?

Started by Corey, Rick November 17, 2003


-----Original Message-----
From: Corey, Rick
Sent: Monday, November 17, 2003 3:27 PM
To: 'TA1T'
Subject: RE: do Ineed to use a timer if using the SPI as a slave? Hi

I don't do the 56827, but if that is a SPI peripheral like the 803-807
peripheral, you never need to set a timer or SCLK when you are the Slave.
The Master does all of that.

Make sure the revision level on your chip is recent enough that it has
working SPI silicon! On the 803, it was only relatively recently that they
got MISO putting out non-corrupt data (rev E??) Some eval boards have
surprisingly old silicon.

By all means put a scope on /SS and make sure it does what you expect - what
you set CPHA to require.

I only had luck with CPHA=0 (meaning TOGGLE BETWEEN EVERY WORD). We have a
consultant who says he got an 807 working with CPHA=1, but I never did. At
least make sure that the Master and Slave SPI setups agree on CPHA and CPOL
and word length, and bit order, etc etc etc. Are you sure you have /SS
connected to both sides without an inverter?

On the scope, is MISO flat, or garbagy?

Rick Corey -----Original Message-----
From: TA1T [mailto:]
Sent: Monday, November 17, 2003 3:01 PM
To:
Subject: do Ineed to use a timer if using the SPI as a slave?
I am using the SPI module on the dsp56f827 as a slave. It reads data
on the MOSI but doesnt send anything back to the master on the
MISO.Do i need to use a quad timer at all. if so WHY,and what
frequency should i set the timer to?