Technical data

MOTOROLA MC68HC912B32
122 MC68HC912B32TS/D
This register can be read or written by BDM commands or firmware.
ENBDM — Enable BDM (permit active background debug mode)
0 = BDM cannot be made active (hardware commands still allowed)
1 = BDM can be made active to allow firmware commands
BDMACT — Background Mode Active Status
0 = BDM not active
1 = BDM active and waiting for serial commands
ENTAG — Instruction Tagging Enable
Set by the TAGGO instruction and cleared when BDM is entered.
0 = Tagging not enabled, or BDM active
1 = Tagging active (BDM cannot process serial commands while tagging is active.)
SDV — Shifter Data Valid
Shows that valid data is in the serial interface shift register. Used by firmware-based instructions.
0 = No valid data
1 = Valid Data
TRACE — Asserted by the TRACE1 instruction
This 16-bit register contains data being received or transmitted via the serial interface.
This 16-bit register is temporary storage for BDM hardware and firmware commands.
This register preserves the content of the CPU12 CCR while BDM is active.
STATUS — BDM Status Register (BDM) $FF01
Bit 7 6 5 4 3 2 1 Bit 0
ENBDM BDMACT ENTAG SDV TRACE 0 0 0
RESET: 0 0 0 1 0 0 0 0
SHIFTER — BDM Shift Register (BDM) $FF02, $FF03
Bit 15 14 13 12 11 10 9 Bit 8
S15 S14 S13 S12 S11 S10 S9 S8
Bit 7 6 5 4 3 2 1 Bit 0
S7 S6 S5 S4 S3 S2 S1 S0
ADDRESS — BDM Address Register (BDM) $FF04, $FF05
Bit 15 14 13 12 11 10 9 Bit 8
A15 A14 A13 A12 A11 A10 A9 A8
Bit 7 6 5 4 3 2 1 Bit 0
A7 A6 A5 A4 A3 A2 A1 A0
CCRSAV — BDM CCR Holding Register (BDM) $FF06
Bit 7 6 5 4 3 2 1 Bit 0
CCR7 CCR6 CCR5 CCR4 CCR3 CCR2 CCR1 CCR0