David Brownell wrote:
No, suppose there're two devices behind the same SPI bus that have
different clock constraints. As active SPI device change may well happen
when each new message is processed, we'll need to set up clocks again
for each message. Right?
Clock is coupled to chipselect/device. When the bus controller
switches to the other device, it updates the clock accordingly.
Yeah, but chipselect is called on per-transfer basis what is likely to
be redundant for clock setting.
Per-message clock configuration is enough AFAIS.
How exactly that's done is system-specific. Many controllers
just have a register per chipselect, listing stuff like SPI mode,
clock divisor, and word size. So switching to that chipselect
kicks those in automatically ... devices ignore the clock unless
they've been selected.
Hmm, usually clocks are configured for the bus not device.
So, summarizing, you haven't convinced me yet. :)
Vitaly
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