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CCS/TMS320F28377D: SCI communication with 335

Part Number: TMS320F28377D

Tool/software: Code Composer Studio

Hi all,

I am trying to get a 77D and 335 to communicate using the SCI peripheral but I'm running into some trouble.

On the 77D I have:

#define CPU_FREQ 150E6
#define LSPCLK_FREQ CPU_FREQ/4
#define SCI_FREQ 100E3
#define SCI_PRD (LSPCLK_FREQ/(SCI_FREQ*8))-1

and on the 335 I have:

#define CPU_FREQ 150E6
#define LSPCLK_FREQ CPU_FREQ/4
#define SCI_FREQ 100E3
#define SCI_PRD (LSPCLK_FREQ/(SCI_FREQ*8))-1

Which should give me the same baud rate on both controllers.  I am using interrupt driven RX and TX on both, and when they are crossed (335RX > 77DTX : 77DRX > 335TX) neither RX interrupts gets triggered.

However if I connect them as (77DTX > 77DRX : 335TX > 335RX) they function as I would expect.  

Does anyone have any suggestions as to what could cause this issue.