Background Debug Module (S12SBDMV1)
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.
Table 5-4. Hardware Commands
Opcode
(hex)
Command
Data
Description
BACKGROUND
90
None
Enter background mode if BDM is enabled. If enabled, an ACK will be issued
when the part enters active background mode.
ACK_ENABLE
ACK_DISABLE
READ_BD_BYTE
D5
D6
E4
None
None
Enable Handshake. Issues an ACK pulse after the command is executed.
Disable Handshake. This command does not issue an ACK pulse.
16-bit address Read from memory with standard BDM firmware lookup table in map.
16-bit data out Odd address data on low byte; even address data on high byte.
READ_BD_WORD
READ_BYTE
EC
E0
E8
C4
CC
C0
C8
16-bit address Read from memory with standard BDM firmware lookup table in map.
16-bit data out Must be aligned access.
16-bit address Read from memory with standard BDM firmware lookup table out of map.
16-bit data out Odd address data on low byte; even address data on high byte.
READ_WORD
WRITE_BD_BYTE
WRITE_BD_WORD
WRITE_BYTE
WRITE_WORD
NOTE:
16-bit address Read from memory with standard BDM firmware lookup table out of map.
16-bit data out Must be aligned access.
16-bit address Write to memory with standard BDM firmware lookup table in map.
16-bit data in Odd address data on low byte; even address data on high byte.
16-bit address Write to memory with standard BDM firmware lookup table in map.
16-bit data in Must be aligned access.
16-bit address Write to memory with standard BDM firmware lookup table out of map.
16-bit data in Odd address data on low byte; even address data on high byte.
16-bit address Write to memory with standard BDM firmware lookup table out of map.
16-bit data in Must be aligned access.
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.
5.4.4
Standard BDM Firmware Commands
BDM 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 5.4.2, “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 0x3_FF00–0x3_FFFF, 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 5-5.
S12P-Family Reference Manual, Rev. 1.13
140
Freescale Semiconductor
FREESCALE [ Freescale ]
