Datasheet

Chapter 6 Background Debug Module (BDMV4) Block Description
176 MC9S12C-Family / MC9S12GC-Family Freescale Semiconductor
Rev 01.24
The BDM hardware commands are listed in Table 6-5.
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.
The READ_BD and WRITE_BD commands allow access to the BDM register locations. These locations
are not normally in the system memory map but share addresses with the application in memory. To
distinguish between physical memory locations that share the same address, BDM memory resources are
enabled just for the READ_BD and WRITE_BD access cycle. This allows the BDM to access BDM
locations unobtrusively, even if the addresses conflict with the application memory map.
6.4.4 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 6.4.2, “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 0xFF00–0xFFFF, and the CPU begins executing the standard BDM
Table 6-5. 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.