mc68hc908gr16 Freescale Semiconductor, Inc, mc68hc908gr16 Datasheet - Page 237

• Manufacturer Part Number: mc68hc908gr16
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Chapter 19
Development Support
19.1 Introduction
This section describes the break module, the monitor read-only memory (MON), and the monitor mode
entry methods.
19.2 Break Module (BRK)
This subsection describes the break module. The break module can generate a break interrupt that stops
normal program flow at a defined address to enter a background program.
Features of the break module include:
19.2.1 Functional Description
When the internal address bus matches the value written in the break address registers, the break module
issues a breakpoint signal (BKPT) to the system integration module (SIM). The SIM then causes the CPU
to load the instruction register with a software interrupt instruction (SWI) after completion of the current
CPU instruction. The program counter vectors to $FFFC and $FFFD ($FEFC and $FEFD in monitor
mode).
The following events can cause a break interrupt to occur:
When a CPU generated address matches the contents of the break address registers, the break interrupt
begins after the CPU completes its current instruction. A return-from-interrupt instruction (RTI) in the
break routine ends the break interrupt and returns the microcontroller unit (MCU) to normal operation.
Figure 19-1
Figure 19-2
Freescale Semiconductor
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Accessible input/output (I/O) registers during the break Interrupt
Central processor unit (CPU) generated break interrupts
Software-generated break interrupts
Computer operating properly (COP) disabling during break interrupts
A CPU generated address (the address in the program counter) matches the contents of the break
address registers.
Software writes a 1 to the BRKA bit in the break status and control register.
shows the structure of the break module.
provides a summary of the I/O registers.
MC68HC908GR16 Data Sheet, Rev. 5.0
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