MC68HC912B32 Datasheet, PDF (120/128 Pages) Motorola, Inc – 16-Bit Microcontroller

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 44 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
16.2.4 BDM Registers
Seven BDM registers are mapped into the standard 64-Kbyte address space when BDM is active. The
registers can be accessed with the hardware READ_BD and WRITE_BD commands, but must not be
written during BDM operation. Most users will only be interested in the STATUS register at $FF01; other
registers are only for use by BDM firmware and logic.
The instruction register is discussed for two conditions: when a hardware command is executed and
when a firmware command is executed.
INSTRUCTION — BDM Instruction Register (hardware command bit explanation)
Bit 7
6
5
4
3
2
1
H/F
DATA
R/W BKGND W/B
BD/U
0
(BDM) $FF00
Bit 0
0
The bits in the BDM instruction register have the following meanings when a hardware command is
executed.
H/F — Hardware/Firmware Flag
0 = Firmware instruction
1 = Hardware instruction
DATA — Data Flag
0 = No data
1 = Data included in command
R/W — Read/Write Flag
0 = Write
1 = Read
BKGND — Hardware request to enter active background mode
0 = Not a hardware background command
1 = Hardware background command (INSTRUCTION = $90)
MOTOROLA
120
MC68HC912B32
MC68HC912B32TS/D