Freescale Semiconductor, Inc.
BREAKPOINT OPERATION FLOW
EXTERNAL DEVICE
PROCESSOR
ACKNOWLEDGE BREAKPOINT
IF BREAKPOINT INSTRUCTION EXECUTED:
1. SET R/W TO READ
2. SET FUNCTION CODE TO CPU SPACE
3. PLACE CPU SPACE TYPE 0 ON A19–A16
4. PLACE BREAKPOINT NUMBER ON A2–A4
5. CLEAR T-BIT (A1)
6. SET SIZE TO WORD
7. ASSERT AS AND DS
IF BKPT PIN ASSERTED:
1. SET R/W TO READ
2. SET FUNCTION CODE TO CPU SPACE
3. PLACE CPU SPACE TYPE 0 ON A19–A16
4. PLACE ALL ONE'S ON A4–A2
5. SET T-BIT (A-1) TO ONE
6. SET SIZE TO WORD
7. ASSERT AS AND DS
IF BREAKPOINT INSTRUCTION EXECUTED:
1. PLACE REPLACEMENT OPCODE ON DATA BUS
2. ASSERT DSACKx
-OR-
1. ASSERT BERR TO INITIATE EXCEPTION PROCESSING
IF BKPT PIN ASSERTED:
1. ASSERT DSACKx
-OR-
1. ASSERT BERR TO INITIATE EXCEPTION PROCESSING
IF BREAKPOINT INSTRUCTION EXECUTED AND
DSACKx IS ASSERTED:
1. LATCH DATA
2. NEGATE AS AND DS
3. GO TO (A)
IF BKPT PIN ASSERTED AND DSACKx IS ASSERTED:
1. NEGATE AS AND DS
2. GO TO (A)
IF BERR ASSERTED:
1. NEGATE AS AND DS
2. GO TO (B)
(A)
(B)
1. NEGATE DSACKx or BERR
IF BREAKPOINT INSTRUCTION EXECUTED:
1. PLACE LATCHED DATA IN INSTRUCTION PIPELINE
2. CONTINUE PROCESSING
IF BKPT PIN ASSERTED:
1. CONTINUE PROCESSING
IF BREAKPOINT INSTRUCTION EXECUTED:
1. INITIATE ILLEGAL INSTRUCTION PROCESSING
IF BKPT PIN ASSERTED:
1. INITIATE HARDWARE BREAKPOINT PROCESSING
Figure 3-11. Breakpoint Operation Flowchart
3- 24
MC68340 USER’S MANUAL
MOTOROLA
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