Datasheet

Breakpoints
M68HC12B Family Data Sheet, Rev. 9.1
Freescale Semiconductor 299
18.3.8 BDM Address Register
The 16-bit ADDRESS register is temporary storage for BDM hardware and firmware commands. The
register can be read in all modes but is not normally accessed by users. It is written only by BDM
hardware.
18.3.9 BDM CCR Holding Register
The CCRSAV register is used to save the state of the condition code register (CCR) of the user’s program
when entering BDM. It is also used for temporary storage in the BDM firmware. The register is initialized
by the firmware to equal the CPU CCR register.
18.4 Breakpoints
Hardware breakpoints are used to debug software on the MCU by comparing actual address and data
values to predetermined data in setup registers. A successful comparison places the CPU in background
debug mode (BDM) or initiates a software interrupt (SWI).
Breakpoint features designed into the MCU include:
• Mode selection for BDM or SWI generation
• Program fetch tagging for cycle of execution breakpoint
• Second address compare in dual address modes
• Range compare by disable of low byte address
• Data compare in full feature mode for non-tagged breakpoint
• Byte masking for high/low byte data compares
•R/W
compare for non-tagged compares
• Tag inhibit on BDM TRACE
Address: $FF04
Bit 7654321Bit 0
Read:
A15 A14 A13 A12 A11 A10 A9 A8
Write:
Reset:00000000
Address: $FF05
Bit 7654321Bit 0
Read:
A7 A6 A5 A4 A3 A2 A1 A0
Write:
Reset:00000000
Figure 18-8. BDM Address Register (ADDRESS)
Address: $FF06
Bit 7654321Bit 0
Read:
CCR7 CCR6 CCR5 CCR4 CCR3 CCR2 CCR1 CCR0
Write:
Reset:00000000
Figure 18-9. BDM CCR Holding Register (CCRSAV)