Motorola M68000 User Manual page 44

BUS MASTER
ADDRESS THE DEVICE
1) SET R/W TO READ
2) PLACE FUNCTION CODE ON FC2–FC0
3) PLACE ADDRESS ON A23–A0
4) ASSERT ADDRESS STROBE (AS)
5) ASSERT LOWER DATA STROBE (LDS)
(DS ON MC68008)
ACQUIRE THE DATA
1) LATCH DATA
1) NEGATE LDS OR DS
2) START DATA MODIFICATION
START OUTPUT TRANSFER
1) SET R/W TO WRITE
2) PLACE DATA ON D7–D0
3) ASSERT LOWER DATA STROBE (LDS)
(DS ON MC68008)
TERMINATE OUTPUT TRANSFER
1) NEGATE DS OR LDS
2) NEGATE AS
3) REMOVE DATA FROM D7–D0
4) SET R/W TO READ
START NEXT CYCLE
Figure 4-5. Read-Modify-Write Cycle Flowchart
4-6 M68000 8-/16-/32-BIT MICROPROCESSORS USER'S MANUAL
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SLAVE
INPUT THE DATA
1) DECODE ADDRESS
2) PLACE DATA ON D7–D0
3) ASSERT DATA TRANSFER
ACKNOWLEDGE (DTACK)
TERMINATE THE CYCLE
1) REMOVE DATA FROM D7–D0
2) NEGATE DTACK
INPUT THE DATA
1) STORE DATA ON D7–D0
2) ASSERT DATA TRANSFER
ACKNOWLEDGE (DTACK)
TERMINATE THE CYCLE
1) NEGATE DTACK
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