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Chapter 19 Background Debug Module (S12XBDMV2)
MC9S12XDP512 Data Sheet, Rev. 2.11
776 Freescale Semiconductor
19.4.4 Standard BDM Firmware Commands
Firmware commands are used to access and manipulate CPU resources. The system must be in active
BDM to execute standard BDM firmware commands, see Section 19.4.2, “Enabling and Activating
BDM”. Normal instruction execution is suspended while the CPU executes the firmware located in the
standard BDM firmware lookup table. The hardware command BACKGROUND is the usual way to
activate BDM.
As the system enters active BDM, the standard BDM firmware lookup table and BDM registers become
visible in the on-chip memory map at 0x7FFF00–0x7FFFFF, and the CPU begins executing the standard
BDM firmware. The standard BDM firmware watches for serial commands and executes them as they are
received.
The firmware commands are shown in Table 19-6.
Table 19-5. Hardware Commands
Command
Opcode
(hex)
Data Description
BACKGROUND 90 None Enter background mode if firmware is enabled. If enabled, an ACK will be
issued when the part enters active background mode.
ACK_ENABLE D5 None Enable Handshake. Issues an ACK pulse after the command is executed.
ACK_DISABLE D6 None Disable Handshake. This command does not issue an ACK pulse.
READ_BD_BYTE E4 16-bit address
16-bit data out
Read from memory with standard BDM firmware lookup table in map.
Odd address data on low byte; even address data on high byte.
READ_BD_WORD EC 16-bit address
16-bit data out
Read from memory with standard BDM firmware lookup table in map.
Must be aligned access.
READ_BYTE E0 16-bit address
16-bit data out
Read from memory with standard BDM firmware lookup table out of map.
Odd address data on low byte; even address data on high byte.
READ_WORD E8 16-bit address
16-bit data out
Read from memory with standard BDM firmware lookup table out of map.
Must be aligned access.
WRITE_BD_BYTE C4 16-bit address
16-bit data in
Write to memory with standard BDM firmware lookup table in map.
Odd address data on low byte; even address data on high byte.
WRITE_BD_WORD CC 16-bit address
16-bit data in
Write to memory with standard BDM firmware lookup table in map.
Must be aligned access.
WRITE_BYTE C0 16-bit address
16-bit data in
Write to memory with standard BDM firmware lookup table out of map.
Odd address data on low byte; even address data on high byte.
WRITE_WORD C8 16-bit address
16-bit data in
Write to memory with standard BDM firmware lookup table out of map.
Must be aligned access.
NOTE:
If enabled, ACK will occur when data is ready for transmission for all BDM READ commands and will occur after the write is
complete for all BDM WRITE commands.