Motorola MC68030 User Manual page 203

CONTROLLER
LOCK BUS
1) ASSERT READ-MODIFY-WRITE CYCLE
(RMC)
START INPUT TRANSFER
1) ASSERT ECS/OCS FOR ONE-HALF CLOCK
2) DRIVE R/W TO READ
3) DRIVE FUNCTION CODE ON FC2–FC0
4) DRIVE ADDRESS ON A31–A0
5) DRIVE SIZE (SIZ1–SIZ0)
6) CACHE INHIBIT OUT (CIOUT) BECOMES
VALID
7) ASSERT ADDRESS STROBE (AS)
8) ASSERT DATA STROBE (DS)
9) ASSERT DATA BUFFER ENABLE (DBEN)
TERMINATE INPUT TRANSFER
1) SAMPLE CACHE INHIBIT IN (CIIN)
2) LATCH DATA
3) NEGATE AS AND DS
4) NEGATE DBEN
5) START DATA MODICIATION
START OUTPUT TRANSFER
1) ASSERT ECS/OCS FOR ONE-HALF CLOCK
2) SET R/W TO WRITE
3) DRIVE ADDRESS ON A31–A0 (IF DIFFERENT)
4) DRIVE SIZE (SIZ1–SIZ0)
5) CIOUT BECOMES VALID
6) ASSERT AS
7) ASSERT DBEN
8) PLACE DATA ON D31–D0
9) ASSERT DS (IF WAIT STATES)
TERMINATE OUTPUT TRANSFER
1) NEGATE AS (AND DS)
2) REMOVE DATA FROM D31–D0
3) NEGATE DBEN
UNLOCK BUS
1) NEGATE RMC
START NEXT CYCLE
Figure 7-35. Synchronous Read-Modify-Write Cycle Flowchart
MOTOROLA
EXTERNAL DEVICE
PRESENT DATA
1) DECODE ADDRESS
2) PLACE DATA ON D31-D0
3) ASSERT SYNCHRONOUS
TERMINATION (STERM)
TERMINATE CYCLE
1) REMOVE DATA FROM D31–D0
2) NEGATE STERM
ACCEPT DATA
1) DECODE ADDRESS
2) STORE DATA FROM D31-D0
3) ASSERT STERM
TERMINATE CYCLE
1) NEGATE STERM
MC68030 USER'S MANUAL
Bus Operation
A
IF CAS2 INSTRUCTION
AND ONLY ONE OPERAND
READ, THEN GO TO A :
IF OPERANDS DO NOT
MATCH, THEN GO TO C :
ELSE GO TO B
C
B
D
IF CAS2 INSTRUCTION
AND ONLY ONE
OPERAND
WRITTEN, THEN GO TO
D : ELSE GO TO E
E
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