
CPU32
REFERENCE MANUAL
DEVELOPMENT SUPPORT
MOTOROLA
7-1
SECTION 7 DEVELOPMENT SUPPORT
All M68000 Family members have the following special features that facilitate applica-
tions 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, allow-
ing a debugger program to monitor execution of a program under test. See
6.2.10
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
6.2.5 Software Breakpoints
for
more information.
Unimplemented Instruction Emulation — When an attempt is made to execute an
illegal instruction, an illegal instruction exception occurs. Unimplemented instruc-
tions (F-line, A-line) utilize separate exception vectors to permit efficient emulation
of unimplemented instructions in software. See
6.2.8 Illegal or Unimplemented
Instructions
for more information.
7.1 CPU32 Integrated Development Support
In addition to standard MC68000 family capabilities, the CPU32 has features to sup-
port advanced integrated system development. These features include background
debug mode, deterministic opcode tracking, hardware breakpoints, and internal visi-
bility in a single-chip environment.
7.1.1 Background Debug Mode (BDM) Overview
Microprocessor systems generally provide a debugger, implemented in software, for
system analysis at the lowest level. The BDM on the CPU32 is unique because the
debugger is implemented in CPU microcode.
BDM incorporates a full set of debug options — registers can be viewed and/or altered,
memory can be read or written, and test features can be invoked.
A resident debugger simplifies implementation of an in-circuit emulator. In a common
setup (see
Figure 7-1
), emulator hardware replaces the target system processor. A
complex, expensive pod-and-cable interface provides a communication path between
target system and emulator.
By contrast, an integrated debugger supports use of a bus state analyzer (BSA) for in-
circuit emulation. The processor remains in the target system (see
Figure 7-2
) and the
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n
.