Hi all,
In SPI interface if i see there are two signals cpol and cpha, which are used for differnet data transfer formats. What i wanted to know is why 4 different data transfer formats have been defined??? If both the master and slave agreed upon one format that shoud be fine right.
Any suggestions are appreciated.
Thanks in advance, Praveen
On 15 May 2005 22:41:09 -0700, snipped-for-privacy@gmail.com wroth:
There are four formats because that is the number of combinations available for two variables each with two states.
That would be fine, but boring.
The SPI "standard" was not always a standard. In the beginning, there were two or more manufacturers making chips that used similar, but different, serial connection schemes. In an effort to make the chips appear to be usable between manufacturers, the SPI standard was defined. The four cpol/cpha combinations were defined so that each manufacturer could claim conformance to the "standard" without having to actually change their established chip architecture.
If you thing the cpol/cpha thing is strange, take a look at the different specifications for number of bits per "word" on the data lines.
Jim
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