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MC68HC812A4 Datasheet, PDF (313/342 Pages) Motorola, Inc – 16-bit device composed of standard on-chip peripheral modules connected by an intermodule bus. Modules include
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Development Support
Background Debug Mode (BDM)
Table 17-2. BDM Commands Implemented in Hardware (Continued)
Command
Opcode (Hex)
Data
Description
ENABLE_
FIRMWARE(2)
Write byte $FF01, set the ENBDM bit. This allows
C4
FF01,
execution of commands which are implemented in
1xxx xxxx (in) firmware. Typically, read STATUS, OR in the MSB,
write the result back to STATUS.
WRITE_BD_WORD
CC
16-bit address Write to memory with BDM in map (may steal cycles
16-bit data in if external access); must be aligned access
WRITE_BYTE
C0
16-bit address
16-bit data in
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_WORD
C8
16-bit address Write to memory with BDM out of map (may steal
16-bit data in cycles if external access); must be aligned access
1. STATUS command is a specific case of the READ_BD_BYTE command.
2. ENABLE_FIRMWARE is a specific case of the WRITE_BD_BYTE command.
Command
READ_NEXT
READ_PC
READ_D
READ_X
READ_Y
READ_SP
WRITE_NEXT
WRITE_PC
WRITE_D
WRITE_X
WRITE_Y
WRITE_SP
GO
TRACE1
TAGGO
Table 17-3. BDM Firmware Commands
Opcode (Hex)
62
63
64
65
66
67
42
43
44
45
46
47
08
10
18
Data
16-bit data out
16-bit data out
16-bit data out
16-bit data out
16-bit data out
16-bit data out
16-bit data in
16-bit data in
16-bit data in
16-bit data in
16-bit data in
16-bit data in
None
None
None
Description
X = X + 2; read next word pointed to by X
Read program counter
Read D accumulator
Read X index register
Read Y index register
Read stack pointer
X = X + 2; write next word pointed to by X
Write program counter
Write D accumulator
Write X index register
Write Y index register
Write stack pointer
Go to user program
Execute one user instruction, then return to BDM
Enable tagging and go to user program
Advance Information
MOTOROLA
Development Support
MC68HC812A4 — Rev. 3.0
313
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