I have a device which uses two DSP56F805, and they are DSP-A and DSP-B. Several days ago, I can't download the program onto DSP-B (at the beginning, not after several percentages). In most cases, Codewarrior mentions "Failed to erase flash", sometimes mentions "Unknown protocol Error". This problem occasionally came up in DSP-A, but usually it works. Then I came up with the question “Failed to erase flash”, and I was told that DSP-B might have a damage, so I changed the chip. But now, it still doesn't work, and codewarrior mentions "Unknown Protocol Error". I have checked the JTAG interface of DSP-B, I think there is no problem. I also download the program of DSP-B onto DSP-A, so I think the cable and the program should have no problem. I really don't know where the problem might be. Please help me, I am almost lose the hopes.