MC68HC12 MOTOROLA [Motorola, Inc], MC68HC12 Datasheet - Page 402

• Manufacturer Part Number: MC68HC12
• Description: The MC68HC912DT128A microcontroller unit (MCU) is a 16-bit device composed of standard on-chip peripherals including a 16-bit central processing unit
• Manufacturer: MOTOROLA [Motorola, Inc]

Development Support
Technical Data
402
WRITE_BD_WORD
READ_BD_WORD
WRITE_BD_BYTE
1. Use these commands only for reading/writing to BDM locations
READ_BD_BYTE
BACKGROUND
mally in the HC12 MCU memory map
memory map, there needs to be a way to decide which physical locations are being accessed by the hardware BDM com-
mands
application locations
cycles of the READ_BD and WRITE_BD commands
BDM locations even if the application program is running out of the same memory area in the normal application memory
map
WRITE_WORD
READ_WORD
WRITE_BYTE
READ_BYTE
Command
.
.
This gives rise to needing separate memory access commands for the BDM locations as opposed to the normal
(1)
(1)
(1)
(1)
.
In logic, this is accomplished by momentarily enabling the BDM memory resources, just for the access
Opcode (Hex)
The second type of BDM commands are called 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 while BDM
is active. The CPU executes code in the BDM firmware to perform the
requested operation. The BDM firmware watches for serial commands
EC
CC
C4
C0
C8
E4
E0
E8
90
Table 20-2. Hardware Commands
.
Since these locations have the same addresses as some of the normal application
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
None
Development Support
Data
.
This logic allows the debugging system to unobtrusively access the
Enter background mode if firmware enabled.
Read from memory with BDM in map (may steal cycles
Read from memory with BDM in map (may steal cycles
Read from memory with BDM out of map (may steal
Read from memory with BDM out of map (may steal
Write to memory with BDM in map (may steal cycles if
Write to memory with BDM in map (may steal cycles if
Write to memory with BDM out of map (may steal cycles
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.
if external access). Must be aligned access.
cycles if external access) data for odd address on low
byte, data for even address on high byte.
cycles if external access). Must be aligned access.
external access) data for odd address on low byte,
data for even address on high byte.
external access). Must be aligned access.
if external access) data for odd address on low byte,
data for even address on high byte.
if external access). Must be aligned access.
.
The BDM firmware ROM and BDM registers are not nor-
(1)
Description
MC68HC912DT128A — Rev 4.0
MOTOROLA