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SPI and 56F8xx: Brain Dead?

Started by drjohn_online December 29, 2003
Hi,
Has anyone ever got a 56F801 to work as an SPI slave?

After weeks of trying, all I get are semi-random garbage chars in the
receive register after SPRF is set. I checked the chip errata but
none described this problem.

The scenario:
56F801 date code 0310
SPI slave, CPOL=0, CPHA=0, 8-bits
ISR or polled: same problem.
Slow/Fast: same problem.
8- or 16-bits: same problem.
The waveform is golden.

Interesting:
I am hitting the slave with the same data byte (0xaa) repeatedly.
Semi-random chars come out of the SPDRR. Often SPRF is set two or
three times for each transmission. There *is* some dependence on the
data: if I send 0x00, it works fine. Anything else gives garbage.
Interestingly, the received bytes are always strings of ones and
zeroes. e.g., xf8, x3c, 0x1f or something similar. Never solitary
ones or zeroes, e.g. 0xaa, 0x52, 0x16. It almost looks like the
receiver is clocking itself at some rate higher than SCLK and
oversampling the MOSI stream (just a theory).

If anyone has a suggestion, experience or code sniplet, I will be
*eternally* grateful.

Best Regards
John Wilson



I tried....but not successfully. My 56F801 evaluation board never works as
SPI slave.
I check the data code of the chip and is old silicon with SPI problems. My
first prototype board has old silicon too, and slave SPI is not working.
In both cases, there are data shifts, and the communication fail.
Please see the message from Rick Corey - RE: [motoroladsp] Can't get SPI to
work - October 21 (is very clear about this)

Best Regards
Luis Motrel ----- Mensaje original -----
De: "drjohn_online" <>
Para: <>
Enviado: Lunes, 29 de Diciembre de 2003 16:52
Asunto: [motoroladsp] SPI and 56F8xx: Brain Dead? > Hi,
> Has anyone ever got a 56F801 to work as an SPI slave?
>
> After weeks of trying, all I get are semi-random garbage chars in the
> receive register after SPRF is set. I checked the chip errata but
> none described this problem.
>
> The scenario:
> 56F801 date code 0310
> SPI slave, CPOL=0, CPHA=0, 8-bits
> ISR or polled: same problem.
> Slow/Fast: same problem.
> 8- or 16-bits: same problem.
> The waveform is golden.
>
> Interesting:
> I am hitting the slave with the same data byte (0xaa) repeatedly.
> Semi-random chars come out of the SPDRR. Often SPRF is set two or
> three times for each transmission. There *is* some dependence on the
> data: if I send 0x00, it works fine. Anything else gives garbage.
> Interestingly, the received bytes are always strings of ones and
> zeroes. e.g., xf8, x3c, 0x1f or something similar. Never solitary
> ones or zeroes, e.g. 0xaa, 0x52, 0x16. It almost looks like the
> receiver is clocking itself at some rate higher than SCLK and
> oversampling the MOSI stream (just a theory).
>
> If anyone has a suggestion, experience or code sniplet, I will be
> *eternally* grateful.
>
> Best Regards
> John Wilson >
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