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AT89S52 Write lock sequence

Praveen Kumar R

I'm designing an ISP programmer for AT89S52. I have completed Erase,Write & verify successfully but I'm stuck with programming the lock bits. I want to achieve write lock mode 2.

I'm sending the sequence: 0xAC 0xE0 0x00 0x00 0xAC 0xE1 0x00 0x00 0xAC 0xE2 0x00 0x00 0xAC 0xE3 0x00 0x00

To read the lock bits, 0x24 0x00 0x00 0x00

During the read lock bits sequence, it reads back 0x01, so only mode 1 is activated. What am I doing wrong?