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SPI Mode for the ADS8509

 
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sir_jfreyes



Joined: 10 Aug 2009
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SPI Mode for the ADS8509
PostPosted: Mon Mar 22, 2010 10:05 am     Reply with quote
Hello everybody, someone could help me to identify the operating mode SPI for the ADS8509?

http://focus.ti.com/lit/ds/symlink/ads8509.pdf
PCM programmer



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PostPosted: Mon Mar 22, 2010 12:49 pm     Reply with quote
To try to make the ADS8509 interface be as SPI-like as possible, I think
you want to use the method shown in this diagram in the data sheet:
Quote:

Figure 4. Read After Conversion (Discontinuous External DATACLK)

That diagram shows that data changes on the rising edge of the external
clock, so presumably you would sample (in the PIC) on the falling edge.

Also, on page 17 of the data sheet, it says:
Quote:

In this discontinuous external clock mode with no SYNC, 16 clocks are
necessary to read the data on the falling edge.

This means data is sampled (by the PIC) on the falling edge.
That's confirmed.

Figure 4 in the data sheet also shows that the external clock idles at a
low level.

Now look at the SPI modes diagram on this page:
http://www.totalphase.com/support/kb/10045/#modes
It's clear that Mode 1 idles at a low level and samples on the falling edge,
so that's the mode to use.
sir_jfreyes



Joined: 10 Aug 2009
Posts: 6

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PostPosted: Wed Mar 24, 2010 10:55 pm     Reply with quote
Thanks a lot for help me and take time for do it.
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