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M68000 8-/16-/32-BIT MICROPROCESSORS USER'S MANUAL
MOTOROLA
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)
TERMINATE THE CYCLE
INPUT THE DATA
1) DECODE ADDRESS
2) PLACE DATA ON D7–D0
3) ASSERT DATA TRANSFER
ACKNOWLEDGE (DTACK)
SLAVE
START NEXT CYCLE
1) REMOVE DATA FROM D7–D0
2) NEGATE DTACK
1) LATCH DATA
1) NEGATE LDS OR DS
2) START DATA MODIFICATION
ACQUIRE THE DATA
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
INPUT THE DATA
1) STORE DATA ON D7–D0
2) ASSERT DATA TRANSFER
ACKNOWLEDGE (DTACK)
TERMINATE THE CYCLE
1) NEGATE DTACK
Figure 4-5. Read-Modify-Write Cycle Flowchart
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Freescale Semiconductor, Inc.
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