SPI - spikes on the MOSI line between frames

sjpatel19922 · ‎2017-05-16

Posted on May 16, 2017 at 22:15

Hi, I am using the

SPC570S40E1 microcontroller. When looking at the MOSI line on the scope, I am seeing spikes right around the end of a frame even when transmitting all zeros. The device I am trying to communicate with requires a 40 bit message. To achieve that, I am sending 16,16 and 8 bit frames.

There is one spike at beginning of the second frame and another at the beginning of the third frame.

Also, regarding the Fast Continuous PC mode, which allows masking the Tasc and Tcsc delays, is there a way to enable the masking of delays without also enabling parity bit transmission.

Thanks

Update: I don't see any spikes if I enable continuous clock, but I am still looking for a solution without having to do that. I tried lowering the baud rate and adjusting the delays( Tasc and Tcsc), but that didn't work.

#spi

Erwan YVIN · ‎2017-05-17

Posted on May 17, 2017 at 16:10

Hello ,

After checking with experts, I think that it is not possible

The delays can be masked in Fast Continuous PC mode

1 Fast Continuous PCS mode. Delays masked via control bits in PUSHR.

cf bit PE_MASC

Parity Enable or Mask tASC delay in the current frame PE

This bit enables parity bit transmission and parity reception check for the SPI frame.

Best regards

Erwan