For selecting one of two devices it is certainly feasible to use the /SS pin to select one device when the signal is low and the other when the signal is high, provided that the pin is software controllable as an output. Some SPI peripherals have high active select inputs and others have low true select pins. If both of your devices have select inputs that are of the same active level then you would have to add an inverter to flip the sense of the /SS signal for one of the devices.

Please note it is important to study the data sheet to make sure that the /SS pin is actually available as an output on your part. Some SPI interfaces just use this as the select input to the processor when the processor SPI is being used in SLAVE mode. You of course will be interfacing to the A/D and D/A with the processor in MASTER mode.

Finally note that your best source of information is the ATMEL web site. Use of the following link can also provide much information...




Michael Karas