M68000 datasheet(51/189 Pages) FREESCALE

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MOTOROLA

M68000 8-/16-/32-BIT MICROPROCESSORS USER'S MANUAL

5- 5

The word and byte write-cycle timing diagram and flowcharts in Figures 5-5, 5-6, and 5-7

applies directly to the MC68000, the MC68HC000, the MC68HC001 (in 16-bit mode), the

MC68EC000 (in 16-bit mode), and the MC68010.

BUS MASTER

ADDRESS THE DEVICE

1) PLACE FUNCTION CODE ON FC2–FC0

2) PLACE ADDRESS ON A23–A1

3) ASSERT ADDRESS STROBE (AS)

4) SET R/W TO WRITE

5) PLACE DATA ON D15–D0

6) ASSERT UPPER DATA STROBE (UDS)

AND LOWER DATA STROBE (LDS)

TERMINATE THE CYCLE

INPUT THE DATA

1) DECODE ADDRESS

2) STORE DATA ON D15–D0

3) ASSERT DATA TRANSFER

ACKNOWLEDGE (DTACK)

SLAVE

START NEXT CYCLE

1) NEGATE DTACK

TERMINATE OUTPUT TRANSFER

1) NEGATE UDS AND LDS

2) NEGATE AS

3) REMOVE DATA FROM D15–D0

4) SET R/W TO READ

Figure 5-5. Word Write-Cycle Flowchart

BUS MASTER

ADDRESS THE DEVICE

1) PLACE FUNCTION CODE ON FC2–FC0

2) PLACE ADDRESS ON A23–A1

3) ASSERT ADDRESS STROBE (AS)

4) SET R/W TO WRITE

5) PLACE DATA ON D0–D7 OR D15–D8

(ACCORDING TO INTERNAL A0)

6) ASSERT UPPER DATA STROBE (UDS)

OR LOWER DATA STROBE (LDS)

(BASED ON INTERNAL A0)

1) NEGATE UDS AND LDS

2) NEGATE AS

3) REMOVE DATA FROM D7-D0 OR

D15-D8

4) SET R/W TO READ

TERMINATE THE CYCLE

INPUT THE DATA

1) DECODE ADDRESS

2) STORE DATA ON D7–D0 IF LDS IS

ASSERTED. STORE DATA ON D15–D8

IF UDS IS ASSERTED

3) ASSERT DATA TRANSFER

ACKNOWLEDGE (DTACK)

SLAVE

START NEXT CYCLE

TERMINATE OUTPUT TRANSFER

1) NEGATE DTACK

Figure 5-6. Byte Write-Cycle Flowchart

Freescale Semiconductor, Inc.

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