MC68HC12 MOTOROLA [Motorola, Inc], MC68HC12 Datasheet - Page 413

• Manufacturer Part Number: MC68HC12
• Description: The MC68HC912DT128A microcontroller unit (MCU) is a 16-bit device composed of standard on-chip peripherals including a 16-bit central processing unit
• Manufacturer: MOTOROLA [Motorola, Inc]

20.5.1 Breakpoint Modes
20.5.1.1 SWI Dual Address Mode
20.5.1.2 BDM Full Breakpoint Mode
MC68HC912DT128A — Rev 4.0
MOTOROLA
Three modes of operation determine the type of breakpoint in effect.
Breakpoints will not occur when BDM is active.
In this mode, dual address-only breakpoints can be set, each of which
cause a software interrupt. This is the only breakpoint mode which can
force the CPU to execute a SWI. Program fetch tagging is the default in
this mode; data breakpoints are not possible. In the dual mode each
address breakpoint is affected by the BKPM bit and the BKALE bit. The
BKxRW and BKxRWE bits are ignored. In dual address mode the
BKDBE becomes an enable for the second address breakpoint. The
BKSZ8 bit will have no effect when in a dual address mode.
A single full feature breakpoint which causes the part to enter
background debug mode. BDM mode may be entered by a breakpoint
only if an internal signal from the BDM indicates background debug
mode is enabled.
•
•
•
•
•
Dual address-only breakpoints, each of which will cause a
software interrupt (SWI)
Single full-feature breakpoint which will cause the part to enter
background debug mode (BDM)
Dual address-only breakpoints, each of which will cause the part
to enter BDM
Breakpoints are not allowed if the BDM mode is already active.
Active mode means the CPU is executing out of the BDM ROM.
BDM should not be entered from a breakpoint unless the ENABLE
bit is set in the BDM. This is important because even if the
ENABLE bit in the BDM is negated the CPU actually does execute
the BDM ROM code. It checks the ENABLE and returns if not set.
If the BDM is not serviced by the monitor then the breakpoint
would be re-asserted when the BDM returns to normal CPU flow.
Development Support
Development Support
Technical Data
Breakpoints
413