SPI slave select signals

Hi all,

In an SPI interface i have got 4 slaves and one master What i wanted to know is wether the master can assert two slave selects(SS_N) simultaneously OR is there a restriction that master can assert only one slave select.

Does SPI standard dictate anything!!!

Any comments on this would be appreciated.

Regards, Praveen

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The slave will drive its MISO pin while selected.

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Depends on the design of the master. The NIOS II used in the Altera FPGA permits me to asers any number of the SPI select lines.

But also as has been pointed out if the slaves all try to respond with data you've got problems on the SOMI singal line.


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snipped-for-privacy@gmail.com wrote in news:1117455841.370215.303660 @f14g2000cwb.googlegroups.com:

The SPI can certainly assert multiple slave selects. The restriction is on the slaves. No more than one slave can drive the MISO line at the same time.

There are many SPI slave devices that are write only (No MISO connection).


  1. Configuring multiple data converters with the same instructions. You might reset the parts with the same instruction and address the parts independently for gain settings.
Al Clark
Danville Signal Processing, Inc.
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Al Clark

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