mc9s12e256 Freescale Semiconductor, Inc, mc9s12e256 Datasheet - Page 455

• Manufacturer Part Number: mc9s12e256
• Description: Hcs12 Microcontrollers 16-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

NOTE:
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.
15.4.4
Firmware commands are used to access and manipulate CPU resources. The system must be in active
BDM to execute standard BDM firmware commands, see
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
firmware. The standard BDM firmware watches for serial commands and executes them as they are
received.
The firmware commands are shown in
Freescale Semiconductor
READ_WORD
WRITE_BD_BYTE
WRITE_BD_WORD
WRITE_BYTE
WRITE_WORD
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.
Command
Standard BDM Firmware Commands
Opcode
(hex)
CC
E8
C4
C0
C8
Table 15-5. Hardware Commands (continued)
16-bit address
16-bit data out
16-bit address
16-bit address
16-bit address
16-bit address
16-bit data in
16-bit data in
16-bit data in
16-bit data in
Data
MC9S12E256 Data Sheet, Rev. 1.08
Table
15-6.
Read from memory with standard BDM firmware lookup table out of
map. Must be aligned access.
Write to memory with standard BDM firmware lookup table in map. Odd
address data on low byte; even address data on high byte.
Write to memory with standard BDM firmware lookup table in map. Must
be aligned access.
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 to memory with standard BDM firmware lookup table out of map.
Must be aligned access.
Section 15.4.2, “Enabling and Activating
Chapter 15 Background Debug Module (BDMV4)
Description
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