I have been using RA0E1 microcontroller in a custom board, and I need to transmit data into another microcontroller. For that I’m using Simplified SPI, where the RA0E1 controller acts as a slave. I have assigned SI00, SO00 and SCLK00 pins to transmit data. I have kept SSI00 pin open in my circuit board. Now when I am running my circuit on debug mode, I noticed that the callback function is not being called when the SPI transfer takes place. However, the FSP err is being acknowledged as FSP_SUCCESS. Is it necessary to use SSI00 pin to receive command from master, or can we configure this as output low at all times, or just ground that pin?