AM625: MCSPI bidirectional communication with half-duplex

Hello Daisuke,

Thank you for the note and push.

 Refer below input i received from the expert:

However there are two possibilities that I can immediately think of:

 Use a single channel.

1. Writes would work as a normal spi channel
   Reads.  Send command word, change pin configuration, read data.  (CS needs to be manually controlled).
2. Use 2 channels
   Channel A for writes and for read command.
   Channel B for read data
   
   Config needs to change between reads and writes.
   Other than manual control of the CS, the switch between command and read data should be automatic

#1 should work but requires software to manage the change been command a read data.

#2 would need to validated to prove it’s viable.

 Regards,

Sreenivasa

Hello Daisuke,

Thank you.

Please refer the inputs i received from the device expert.

The output buffer associated with output pins of each device will only be enabled when it’s it is sending data and the protocol ensures only one device is driving data at any time.  So the output buffer of the device not driving data will be high-Z.

Regards,

Sreenivasa

Hello Daisuke,

Based on your request below, i am adding the answers as i receive for the IP related questions on the SPI interface

Please give me an answer by Friday morning (Japan time). Your prompt reply would be appreciated.

Here are additional inputs i received. Please read through the inputs 

If the Hi-Z question is in relation to the E2E post, then in order to receive data, you must write data to the Tx buffer, otherwise no spiclk will be generated.   Writing TX data will result in the DO pin driving. Only way to ensure DO  is not driving, is to disable the driver, or configure the signal appropriately in the IP.  Disabling the TX output in the padconfig register would be another (simpler) way of implementing this using a single channel.  The CS would still need to be manually controlled. Automatic control of CS would result in an undesired de-assertion  of the CS between the command word (TX) and the RX data, these would be seen as 2 transactions by our IP.

Regards,

Sreenivasa