Regarding SPI protocol( master)

Hi all,

I have a basic doubt in SPI protocol.Suppose if i have a SPI master
which only transfers data to a slave but does not receive any data
from slave.
Is it possible in SPI protocl to enable only the Transmitter and
disable the receiver.

Thanks in advance,
Prav

prav wrote:

> Hi all,
> 
> I have a basic doubt in SPI protocol.Suppose if i have a SPI master
> which only transfers data to a slave but does not receive any data
> from slave.
> Is it possible in SPI protocl to enable only the Transmitter and
> disable the receiver.

I would consider that the slave should at least send an ACK to indicate 
that it received the transmission OK. However, if your system will live 
without the ACKs then I suppose that missing out the receive section on the 
master would be OK.

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You can ignore the returned data from the slave if you want to and the
data line does not need to be connected. If you were hoping to use the
serial data input pin for something else on your processor then you
might be disappointed. If you study your datasheets carefully then you
may find that selecting SPI mode will allocate that pin.

<hackmode>
If you desperately want to save on I/O pins you could put an unrelated
signal on SDI and clock the data in when you want to read the pin.
</hackmode>

Peter

peterk wrote:

> You can ignore the returned data from the slave if you want to and the
> data line does not need to be connected. If you were hoping to use the
> serial data input pin for something else on your processor then you
> might be disappointed. If you study your datasheets carefully then you
> may find that selecting SPI mode will allocate that pin.

If you wanted to use it as an input for some other signal you may not 
have the same trouble. For example, for AVR, you can still sample PINx 
because the only constraint is that MISO is an input.

> 
> <hackmode>
> If you desperately want to save on I/O pins you could put an unrelated
> signal on SDI and clock the data in when you want to read the pin.
> </hackmode>
> 
> Peter
>