> I have some problems with the project I am working on, and I need your
> help!
>
> 1.      I have 2 devices on the SPI bus (one 16-bit and one 8-bit).
> Each device has its own Chip Select signal.  What I want to do is:
>
> For 16-bit device
>             Select the chip
>             Send 16 bits of data
>             Deselect the chip
>
> For 8-bit device
>             Select the chip
>             Send 8 bits of data
>             Deselect the chip
>
> I have no problem writing the code for multiple 8-bit devices, but when
> it comes to a mixture of 8-bit and 16-bit devices, I am totally stuck.
> I am thinking of using a variable in the ISR to indicate whether it is a
> 8-bit or 16-bit device, but I think it needs Mutual Exclusion.  I am
> using the 16F877.  Please help!

Unless the chip is selected, whatever happens on the clock and data
lines means nothing. [16b]: Just select that chip, send the first
byte/capture
data out, then send the second byte/capture data out, then deselect the
chip.
 [8b]: Just select the chip, send the byte/capture data out, then deselect
the
chip.

> 2.      The SPI module on the 16F877 can be configured to run at
> different speed.  Don't we always want to run it at the fastest speed?

Not quite true. Some SPI devices cannot have a clock faster than 1Mhz
or even 400Khz. At 20Mhz, the fastest SPI is 4Mhz.

> Thank you for your help!
> Best regards,
> Thomas
>
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