Motorola MC68020 - Breakpoint Instruction Flowchart

MOTOROLA M68020 USER’S MANUAL 6- 19
EXIT
ENTRY
INITIATE READ BUS CYCLE
CYCLE TERMINATED WITH
BERR
PIPE STAGE D INSTRUCTION WORD ON DATA BUS
EXECUTE INSTRUCTION WORD
➧
TAKE ILLEGAL INSTRUCTION
EXCEPTION
A19–A16 $0
A4–A2 BREAKPOINT NUMBER
➧
➧
CYCLE TERMINATED WITH
DSACK1/DSACK0
Figure 6-6. Breakpoint Instruction Flowchart
Table 6-4. Exception Priority Groups
Group/
Priority Exception and Relative Priority Characteristic
0 0.0—Reset Aborts all processing (instruction or exception) and
does not save old context.
1 1.0—Address Error
1.1—Bus Error
Suspends processing (instruction or exception) and
saves internal context.
2 2.0—BKPT, CALLM, CHK, CHK2,
cp Midinstruction, cp Protocol Violation,
cpTRAPcc, Divide by Zero, RTE, RTM,
TRAP, TRAPcc, TRAPV
Exception processing is part of instruction execution.
3 3.0—Illegal Instruction, Line A, Unimplemented
Line F, Privilege Violation, cp Preinstruction
Exception processing begins before instruction is
executed.
4 4.0—cp Postinstruction
4.1—Trace
4.2—Interrupt
Exception processing begins when current instruction
or previous exception processing has completed.
NOTE: 0.0 is the highest priority; 4.2 is the lowest.