We are using the MPC8270 FCC channel to communicate over the Ethernet. The transmit and receive frames are corrupted by the FCC in a specific way. After a long cycle of debugging, we think the problem occurs when the CPM reads the data from the Transmit FIFO.
While reading the frame from the main memory, the CPM uses Tx FIFOs to send this frame to the FCC for further transmission. We noticed that the following happens within the Tx FIFOs of the CPM:
- The first 10 bytes of the frame are correctly transmitted via the Tx FIFO
- In the 2nd cycle the next 16 bytes are replicated and sent as 32 bytes of data
- This means that the first 10+16 = 26 bytes are correct, but the next 16 bytes (27-43) are replicated from the previous 16 bytes (11-26).
Does anyone have a clue why this is happening?