Freescale Semiconductor, Inc.
15
0
SP
+$02
STATUS REGISTER
NEXT INSTRUCTION PROGRAM COUNTER HIGH
NEXT INSTRUCTION PROGRAM COUNTER LOW
+$06
+$08
1
1
0
0
VECTOR OFFSET
FAULTED ADDRESS HIGH
FAULTED ADDRESS LOW
+$0C
+$10
PRE-EXCEPTION STATUS REGISTER
FAULTED EXCEPTION FORMAT/VECTOR WORD
FAULTED INSTRUCTION PROGRAM COUNTER HIGH (SIX WORD FRAME ONLY)
FAULTED INSTRUCTION PROGRAM COUNTER LOW (SIX WORD FRAME ONLY)
INTERNAL TRANSFER COUNT REGISTER
+$14
+$16
1
0
SPECIAL STATUS WORD
Figure 5-17. Format $C—Four- and Six-Word BERR Stack
5.6 DEVELOPMENT SUPPORT
All M68000 family members have the following special features that facilitate applications
development.
Trace on Instruction Execution—All M68000 processors include an instruction-by-
instruction tracing facility to aid in program development. The MC68020, MC68030, and
CPU32 can also trace those instructions that change program flow. In trace mode, an
exception is generated after each instruction is executed, allowing a debugger program to
monitor execution of a program under test. See 5.5.2.10 Tracing for more information.
Breakpoint Instruction—An emulator can insert software breakpoints into target code to
indicate when a breakpoint occurs. On the MC68010, MC68020, MC68030, and CPU32,
this function is provided via illegal instructions ($4848–$484F) that serve as breakpoint
instructions. See 5.5.2.5 Software Breakpoints for more information.
Unimplemented Instruction Emulation—When an attempt is made to execute an illegal
instruction, an illegal instruction exception occurs. Unimplemented instructions (F-line, A-
line) utilize separate exception vectors to permit efficient emulation of unimplemented
instructions in software. See 5.5.2.8 Illegal or Unimplemented Instructions for more
information.
5.6.1 CPU32 Integrated Development Support
In addition to standard MC68000 family capabilities, the CPU32 has features to support
advanced integrated system development. These features include background debug
mode, deterministic opcode tracking, hardware breakpoints, and internal visibility in a
single-chip environment.
MOTOROLA
MC68340 USER’S MANUAL
5- 63
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