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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)
ACQUIRE THE DATA
1) LATCH DATA
2) NEGATE LDS (DS FOR MC68008)
3) NEGATE AS
TERMINATE THE CYCLE
INPUT THE DATA
1) DECODE ADDRESS
2) PLACE DATA ON D7–D0
3) ASSERT DATA TRANSFER
ACKNOWLEDGE (DTACK)
1) REMOVE DATA FROM D7–D0
2) NEGATE DTACK
SLAVE
START NEXT CYCLE
Figure 4-1. Byte Read-Cycle Flowchart
S0 S1 S2 S3 S4 S5 S6 S7 S0 S1 S2 S3 S4 S5 S6 S7 S0 S1 S2 S3 S4
w
w
w
w S5 S6 S7
CLK
FC2–FC0
A23–A0
AS
LDS
R/W
DTACK
D7–D0
READ
WRITE
2 WAIT STATE READ
(DS)
Figure 4-2. Read and Write-Cycle Timing Diagram
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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