Motorola M68000 - Page 48

5- 2 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–A1
4) ASSERT ADDRESS STROBE (AS)
5) ASSERT UPPER DATA STROBE (UDS)
AND LOWER DATA STROBE (LDS)
ACQUIRE THE DATA
1) LATCH DATA
2) NEGATE UDS AND LDS
3) NEGATE AS
TERMINATE THE CYCLE
INPUT THE DATA
1) DECODE ADDRESS
2) PLACE DATA ON D15–D0
3) ASSERT DATA TRANSFER
ACKNOWLEDGE (DTACK)
1) REMOVE DATA FROM D15–D0
2) NEGATE DTACK
SLAVE
START NEXT CYCLE
Figure 5-1. Word Read-Cycle Flowchart
BUS MASTER
ADDRESS THE DEVICE
1) SET R/W TO READ
2) PLACE FUNCTION CODE ON FC2–FC0
3) PLACE ADDRESS ON A23-A1
4) ASSERT ADDRESS STROBE (AS)
5) ASSERT UPPER DATA STROBE (UDS)
OR LOWER DATA STROBE (LDS)
(BASED ON INTERNAL A0)
ACQUIRE THE DATA
1) LATCH DATA
2) NEGATE UDS AND LDS
3) NEGATE AS
TERMINATE THE CYCLE
INPUT THE DATA
1) DECODE ADDRESS
2) PLACE DATA ON D7–D0 OR D15–D8
(BASED ON UDS OR LDS)
3) ASSERT DATA TRANSFER
ACKNOWLEDGE (DTACK)
1) REMOVE DATA FROM D7–D0
OR D15–D8
2) NEGATE DTACK
SLAVE
START NEXT CYCLE
Figure 5-2. Byte Read-Cycle Flowchart
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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