Datasheet

Chapter 5. Debug Support 5-23
Background Debug Mode (BDM)
• Results are returned in the two serial transfer cycles after the memory access
completes. For any command performing a byte-sized memory read operation, the
upper 8 bits of the response data are undefined and the referenced data is returned in
the lower 8 bits. The next command’s opcode is sent to the debug module during the
final transfer. If a memory or register access is terminated with a bus error, the error
status (S = 1, DATA = 0x0001) is returned instead of result data.
5.5.3.3 Command Set Descriptions
The following sections describe the commands summarized in Table 5-17.
NOTE:
The BDM status bit (S) is 0 for normally completed
commands; S = 1 for illegal commands, not-ready responses,
and transfers with bus-errors. Section 5.5.2, “BDM Serial
Interface,” describes the receive packet format.
Motorola reserves unassigned command opcodes for future expansion. Unused command
formats in any revision level perform a
NOP and return an illegal command response.
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