I need to impement a Synchronous Serial Interface (SSI) adapter which is triggered by an external Master Clock (25 bit pulses at 400 kHz + t>20us pause). The SSI Slave device is an encoder which responds to the Master Clock and sends its 25 bit data word. My adapter device needs to read this data in order to interpolate the encoder signal.
I can't use built-in interrupt because latency is too high.
I wonder if I can somehow use the SPI. I know, also from this post http://ez.analog.com/message/16642#16642, that the main problem is the fact that 25 (13 in the reference post) is not a multiple of 8. From that post too I realize that I cannot use PLA as it's limited to 16 bit.
Does anyone know a way to work the problem around?
thanks for the help!