mc68hc908gr8vp Freescale Semiconductor, Inc, mc68hc908gr8vp Datasheet - Page 63

• Manufacturer Part Number: mc68hc908gr8vp
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Chapter 6
Break Module (BRK)
6.1 Introduction
This section 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.
6.2 Features
Features of the break module include:
6.3 Functional Description
When the internal address bus matches the value written in the break address registers, the break module
issues a breakpoint signal to the SIM. The SIM then causes the CPU to load the instruction register with
a software interrupt instruction (SWI). 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
is generated. A return-from-interrupt instruction (RTI) in the break routine ends the break interrupt and
returns the MCU to normal operation.
6.3.1 Flag Protection During Break Interrupts
The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during
the break state.
Freescale Semiconductor
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Accessible input/output (I/O) registers during the break interrupt
CPU-generated break interrupts
Software-generated break interrupts
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 logic 1 to the BRKA bit in the break status and control register.
MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7
Figure 6-1
shows the structure of the break module.
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