Components and Basic Operation
9-7
Synchronous Serial Port
Receiving a word through the serial port typically is done as follows:
1) Data from the DR pin is shifted, bit-by-bit (MSB first), into the receive shift
register (RSR).
2) When the RSR is full, the RSR copies the data to the receive FIFO buffer.
3) The process then does one of two things, depending upon the state of the
receive FIFO buffer:
-
If the receive FIFO buffer is not full, the process repeats from step 1.
-
If the receive FIFO buffer is full (as specified by the FR1 and FR0 bits in
the SSPCR), it sends a receive interrupt (RINT) to the processor to re-
quest servicing.
4) The processor can read the received data from the receive FIFO buffer
through the SDTR.
