mc9s12e256 Freescale Semiconductor, Inc, mc9s12e256 Datasheet - Page 456

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

Chapter 15 Background Debug Module (BDMV4)
1
2
15.4.5
Hardware and firmware BDM commands start with an 8-bit opcode followed by a 16-bit address and/or a
16-bit data word depending on the command. All the read commands return 16 bits of data despite the byte
or word implication in the command name.
456
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
GO_UNTIL
TRACE1
TAGGO
Command
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.
Both WAIT (with clocks to the S12 CPU core disabled) and STOP disable the ACK function. The GO_UNTIL command will not
get an Acknowledge if one of these two CPU instructions occurs before the “UNTIL” instruction. This can be a problem for any
instruction that uses ACK, but GO_UNTIL is a lot more difficult for the development tool to time-out.
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1
BDM Command Structure
8-bit reads return 16-bits of data, of which, only one byte will contain valid
data. If reading an even address, the valid data will appear in the MSB. If
reading an odd address, the valid data will appear in the LSB.
16-bit misaligned reads and writes are not allowed. If attempted, the BDM
will ignore the least significant bit of the address and will assume an even
address from the remaining bits.
Opcode (hex)
0C
62
63
64
65
66
67
42
43
44
45
46
47
08
10
18
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
None
Data
Table 15-6. Firmware Commands
MC9S12E256 Data Sheet, Rev. 1.08
Increment X by 2 (X = X + 2), then read word X points to.
Read program counter.
Read D accumulator.
Read X index register.
Read Y index register.
Read stack pointer.
Increment X by 2 (X = X + 2), then write word to location 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. If enabled, ACK will occur when leaving active
background mode.
Go to user program. If enabled, ACK will occur upon returning to active
background mode.
Execute one user instruction then return to active BDM. If enabled, ACK
will occur upon returning to active background mode.
Enable tagging and go to user program. There is no ACK pulse related to
this command.
NOTE
NOTE
Description
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