MC68306 Motorola, MC68306 Datasheet - Page 40

• Manufacturer Part Number: MC68306
• Description: Integrated EC000 Processor
• Manufacturer: Motorola

that uses the read-modify-write cycle) only operates on bytes. Thus, all read-modify-write
cycles are byte operations. The read-modify-write flowchart is shown in Figure 3-8 and the
timing diagram is shown in Figure 3-9.
3-8
1) SET R/W TO READ
2) PLACE FUNCTION CODE ON FC2–FC0
3) PLACE ADDRESS ON ADDRESS BUS
4) ASSERT ADDRESS STROBE (AS)
5) ASSERT UPPER DATA STROBE (UDS)
1) LATCH DATA
1) NEGATE UDS AND LDS
2) START DATA MODIFICATION
1) SET R/W TO WRITE
2) PLACE DATA ON D7–D0 OR D15–D8
3) ASSERT UPPER DATA STROBE (UDS)
1) NEGATE UDS OR LDS
2) NEGATE AS
3) REMOVE DATA FROM D7–D0 OR
4) SET R/W TO READ
OR LOWER DATA STROBE (LDS)
OR LOWER DATA STROBE (LDS)
D15–D8
TERMINATE OUTPUT TRANSFER
START OUTPUT TRANSFER
ADDRESS THE DEVICE
ACQUIRE THE DATA
START NEXT CYCLE
BUS MASTER
Figure 3-8. Read-Modify-Write Cycle Flowchart
MC68306 USER'S MANUAL
1) REMOVE DATA FROM D7–D0
2) NEGATE DTACK
1) DECODE ADDRESS
2) PLACE DATA ON D7–D0 OR D15–D0
3) ASSERT DATA TRANSFER
1) STORE DATA ON D7–D0 OR D15–D8
2) ASSERT DATA TRANSFER
1) NEGATE DTACK
OR D15–D8
ACKNOWLEDGE (DTACK)
ACKNOWLEDGE (DTACK)
TERMINATE THE CYCLE
TERMINATE THE CYCLE
OUTPUT THE DATA
INPUT THE DATA
SLAVE
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