MC68020 Motorola, MC68020 Datasheet - Page 74

• Manufacturer Part Number: MC68020
• Description: (MC68020 / MC68EC020) MICROPROCESSORS USERS MANUAL
• Manufacturer: Motorola

MOTOROLA
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This step does not apply to the MC68EC020.
For the MC68EC020, A23–A0.
1) ASSERT ECS/OCS FOR ONE-HALF CLOCK
2) SET R/W TO READ
3) DRIVE ADDRESS ON A31–A0
4) DRIVE FUNCTION CODE ON FC2–FC0
5) DRIVE SIZ1, SIZ0 (FOUR BYTES)
6) ASSERT AS
7) ASSERT DS
8) ASSERT DBEN
1) LATCH DATA
2) NEGATE AS AND DS
3) NEGATE DBEN
START NEXT CYCLE
ADDRESS DEVICE
ACQUIRE DATA
PROCESSOR
Figure 5-20. Byte Read Cycle Flowchart
M68020 USER’S MANUAL
1) DECODE ADDRESS
2) PLACE DATA ON D31–D24 OR
3) ASSERT DSACK1/DSACK0
1) REMOVE DATA FROM D31–D0
2) NEGATE DSACK1/DSACK0
(BASED ON A1, A0, AND BUS WIDTH)
EXTERNAL DEVICE
TERMINATE CYCLE
PRESENT DATA
D23–D16 OR
D15–D8 OR
D7–D0
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