mc68hc912dg128 Freescale Semiconductor, Inc, mc68hc912dg128 Datasheet - Page 362

• Manufacturer Part Number: mc68hc912dg128
• Description: M68hc12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Development Support
Technical Data
362
1. Use these commands only for reading/writing to BDM locations
WRITE_BD_WORD
READ_BD_WORD
WRITE_BD_BYTE
READ_BD_BYTE
in the HC12 MCU memory map
map, there needs to be a way to decide which physical locations are being accessed by the hardware BDM commands
gives rise to needing separate memory access commands for the BDM locations as opposed to the normal application lo-
cations
READ_BD and WRITE_BD commands
even if the application program is running out of the same memory area in the normal application memory map
BACKGROUND
WRITE_WORD
READ_WORD
WRITE_BYTE
READ_BYTE
Command
.
In logic, this is accomplished by momentarily enabling the BDM memory resources, just for the access cycles of the
(1)
(1)
(1)
(1)
Opcode (Hex)
The second type of BDM commands are firmware commands
implemented in a small ROM within the HC12 MCU. The CPU must be
in background mode to execute firmware commands. The usual way to
get to background mode is by the hardware command BACKGROUND.
The BDM ROM is located at $FF20 to $FFFF while BDM is active. There
are also seven bytes of BDM registers located at $FF00 to $FF06 when
BDM is active. The CPU executes code in the BDM firmware to perform
the requested operation. The BDM firmware watches for serial
commands and executes them as they are received. The firmware
commands are shown in
Freescale Semiconductor, Inc.
.
Since these locations have the same addresses as some of the normal application memory
EC
CC
C4
C0
C8
90
E4
E0
E8
For More Information On This Product,
Table 18-2. Hardware Commands
.
This logic allows the debugging system to unobtrusively access the BDM locations
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16-bit address
16-bit data out
16-bit address
16-bit address
16-bit data out
16-bit address
16-bit data out
16-bit address
16-bit address
16-bit address
16-bit address
16-bit data out
16-bit data in
16-bit data in
16-bit data in
16-bit data in
Development Support
None
Data
.
Table
The BDM firmware ROM and BDM registers are not normally
Enter background mode if firmware enabled.
Read from memory with BDM in map (may steal
cycles if external access) data for odd address on
low byte, data for even address on high byte.
Read from memory with BDM in map (may steal
cycles if external access). Must be aligned access.
Read from memory with BDM out of map (may steal
cycles if external access) data for odd address on
low byte, data for even address on high byte.
Read from memory with BDM out of map (may steal
cycles if external access). Must be aligned access.
Write to memory with BDM in map (may steal cycles
if external access) data for odd address on low byte,
data for even address on high byte.
Write to memory with BDM in map (may steal cycles
if external access). Must be aligned access.
Write to memory with BDM out of map (may steal
cycles if external access) data for odd address on
low byte, data for even address on high byte.
Write to memory with BDM out of map (may steal
cycles if external access). Must be aligned access.
18-3.
(1)
Description
MC68HC912DG128 — Rev 3.0
MOTOROLA
.
.
This