8.3.8.5 SPI Comparison Function on Received Character

The comparison is only relevant for SPI Client mode (MSTR = 0 in FLEX_US_MR).

In Active mode, the CMP flag in FLEX_SPI_SR is raised. It is set when the received character matches the conditions programmed in the SPI Comparison register (FLEX_SPI_CMPR). The CMP flag is set as soon as FLEX_SPI_RDR is loaded with the new received character. The CMP flag is cleared by reading FLEX_SPI_SR.

The SPI Comparison register can be programmed to provide different comparison methods. These are listed below:

• If VAL1 equals VAL2, then the comparison is performed on a single value and the flag is set to 1 if the received character equals VAL1.
• If VAL1 is strictly lower than VAL2, then any value between VAL1 and VAL2 sets the CMP flag.
• If VAL1 is strictly higher than VAL2, then the flag CMP is set to 1 if any received character equals VAL1 or VAL2.

When FLEX_SPI_MR.CMPMODE is cleared, all received data is loaded in FLEX_SPI_RDR and the CMP flag provides the status of the comparison result.

By setting the CMPMODE bit, the comparison result triggers the start of FLEX_SPI_RDR loading (see the figure below). The trigger condition exists as soon as the received character value matches the conditions defined by VAL1 and VAL2 in FLEX_SPI_CMPR. The comparison trigger event is restarted by writing a 1 to the FLEX_SPI_CR.REQCLR bit.

The value programmed in VAL1 and VAL2 fields must not exceed the maximum value of the received character (see BITS field in SPI Chip Select register (FLEX_SPI_CSR)).