AM62D-Q1: MCSPI SBE (start-bit) behavior in FIFO mode

Gilbert Vellet

Part Number: AM62D-Q1
Other Parts Discussed in Thread: AM5716

I will use the MCSPI in master mode to connect to a peripheral. I wish to use the start-bit (SBE) feature (register MCSPI_CH0CONF bit23 (SBE)) where an extra bit is added to the transmitted word to indicate the start of a transaction.

When transmitting a single word at a time, the feature is self explainatory but not very useful as I could have change the word length instead to acheive the same result

If I use the FIFO mode to transmit multiple words while having the start-bit (SBE) option set to 1, what will be the effect on the transmitted output? The user manual does not cover this case. Logically I assume that only the first word transmitted will have a start-bit added, am I right?

This question applies to AM5716 and AM62D-Q1 as we are still undecided on which device to use in our new design.

Thanks

4 months ago

+1 Stanislav Stilyanov 4 months ago

TI__Mastermind 25080 points

Hi Gilbert,

Gilbert Vellet said:
Logically I assume that only the first word transmitted will have a start-bit added, am I right?

The purpose of this bit is to denote the type of the word it is being attached to - Command or Data. SPI Controller will keep adding a Start bit to every word until SBE is cleared to 0.

Sure, you can extend the word with one bit but this would be a little more burden for software, as you may have to insert the bit value each time before sending, or concatenate the bit value in front of every word stored in RAM/Flash.

Regards,

Stan