Hello,
We are developing an application utilising the FEC of the MPC5777C using the evaluation board MPC5777CEVB. The FEC is operated in the MII-Lite mode and the data cache is deactivated.
Problem description:
When no debugger is attached we have detected no problems for both sending and receiving frames.
But when we attach a Trace32 debugger and add a breakpoint to a called function, e.g., the FEC-send-function, all frames sent by the MCU are marked as defective by the receiver and a CRC/align error is indicated. When the breakpoint is deactivated and the execution resumed everything works again.
This error is visible in the following configurations:
- when the EVB is connected to an Ethernet card of a PC;
- When an external loopback is used utilising a cut cable for which the Rx and Tx pairs are connected. In this case the promiscuous mode (RCR[PROM]) has to be set as well to be able to receive the sent packet. When looking at the Tx and Rx buffers the received message seems to be correct and identical to the sent message. In this case we also detected one error each time the manual break command of the debugger, even if no breakpoint is active.
This problem does not manifest itself when we are using the MII internal loopback as described in the reference manual on page 2486 f..
It is also not present when we add a breakpoint to an uncalled function so that it is never activated.
Question:
- Is there any known interference between the debug module and the FEC?
- Are there any troubleshooting steps which we could try?
Regards,
Bernd
