Datasheet

Development Support
M68HC12B Family Data Sheet, Rev. 9.1
296 Freescale Semiconductor
18.3.5 BDM Instruction Register
This section describes the BDM instruction register under hardware command and firmware command.
18.3.5.1 Hardware Command
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)
W/B — Word/Byte Tansfer Flag
0 = Byte transfer
1 = Word transfer
BD/U — BDM Map/User Map Flag
Indicates whether BDM registers and ROM are mapped to addresses $FF00 to $FFFF in the standard
64-Kbyte address space. Used only by hardware read/write commands.
0 = BDM resources not in map
1 = BDM resources in map
Address: $FF00
Bit 7654321Bit 0
Read:
H/F DATA R/W BKGND W/B BD/U 0 0
Write:
Reset:00000000
Figure 18-4. BDM Instruction Register (INSTRUCTION)