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Languguage OS 2
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Languguage OS II Version 10-94 (Knowledge Media)(1994).ISO
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mcu11
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hc11help.arc
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SPI.001
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1989-11-22
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COMMON SPI QUESTION
===================
Q. I want to ground the SS* input to my SPI subsystem (68HC05C4
or 68HC11). I use it in slave mode only. Using CPHA=0 &
CPOL=0, I get no interrupts from the SPI system. Why not?
A: If CPHA=0, the SPI transfer is not considered to be complete
until the SS* pin goes inactive (high). No interrupt is
generated until the transfer completes. Thus, if you wish to
ground the SS* pin, you must select CPHA=1.