mc68hc908ap8a Freescale Semiconductor, Inc, mc68hc908ap8a Datasheet - Page 289

• Manufacturer Part Number: mc68hc908ap8a
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 21
Break Module (BRK)
21.1 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.
21.2 Features
Features of the break module include:
21.3 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) after completion of the current CPU instruction. The program
counter vectors to $FFFC and $FFFD ($FEFC and $FEFD in monitor mode).
Freescale Semiconductor
Note: Writing a logic 0 clears BW.
$FE0C
$FE0D
$FE00
$FE03
$FE0E
Addr.
•
•
•
•
Accessible input/output (I/O) registers during the break interrupt
CPU-generated break interrupts
Software-generated break interrupts
COP disabling during break interrupts
SIM Break Status Register
Break Status and Control
SIM Break Flag Control
Register Name
Break Address
Break Address
Register High
Register Low
(BRKSCR)
(SBFCR)
Register
Register
(BRKH)
(SBSR)
(BRKL)
Figure 21-1. Break Module I/O Register Summary
Reset:
Reset:
Reset:
Reset:
Reset:
Read:
Write:
Read:
Write:
Read:
Write:
Read:
Write:
Read:
Write:
MC68HC908AP A-Family Data Sheet, Rev. 3
BRKE
BCFE
Bit 15
Bit 7
Bit 7
R
0
0
0
0
= Unimplemented
BRKA
14
R
R
6
0
6
0
0
13
R
R
5
0
5
0
0
0
12
R
R
R
4
0
4
0
0
0
= Reserved
11
R
R
3
0
3
0
0
0
10
R
R
2
0
2
0
0
0
SBSW
Note
R
1
0
9
0
1
0
0
0
Bit 0
Bit 8
Bit 0
R
R
0
0
0
0
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