MC68020 Datasheet, PDF (144/306 Pages) Motorola, Inc – MICROPROCESSORS USERS MANUAL

ENTRY
A19–A16 $0
A4–A2 BREAKPOINT NUMBER
INITIATE READ BUS CYCLE
CYCLE TERMINATED WITH
DSACK1/DSACK0
CYCLE TERMINATED WITH
BERR
PIPE STAGE D INSTRUCTION WORD ON DATA BUS
EXECUTE INSTRUCTION WORD
TAKE ILLEGAL INSTRUCTION
EXCEPTION
EXIT
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 Exception processing begins before instruction is
Line F, Privilege Violation, cp Preinstruction 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.
MOTOROLA
M68020 USER’S MANUAL
6-19