Asynchronous Write Cycle - Motorola MC68030 User Manual

7.3.2 Asynchronous Write Cycle
During a write cycle, the processor transfers data to memory or a peripheral
device.
Figure 7-24 is a flowchart of a write cycle operation for a long-word transfer.
The following figures show the functional write cycle timing diagrams spec-
ified in terms of clock periods. Figure 7-25 shows two write cycles (between
two read cycles with no idle time) for a 32-bit port. Figure 7-26 shows byte
and word write cycles to a 32-bit port. Figure 7-27 shows a long-word write
cycle to an 8-bit port. Figure 7-28 shows a long-word write cycle to a 16-bit
port.
PROCESSOR EXTERNAL OEVICE
AODRESS DEVICE
I} ASSERT ECS/OCS FOR ONE·HALF CLOCK
2} DRIVE ADDRESS ON AO·A31
3} DRIVE FUNCTION CODE ON FCO·FC2
4} DRIVE SIZE (SIZO·SIZ1) (FOUR BYTES)
5} SET R/W TO WRITE
6} CACHE INHIBIT OUT (ClOUT) BECOMES VALID
7} ASSERT ADDRESS STROBE
(AS)
8} ASSERT DATA BUFFER ENABLE (DBEN)
9} DRIVE DATA LINES 00·031
10} ASSERT DATA STROBE
(5s)
:------+
ACCEPT DATA
I} DECODE ADDRESS
2} STORE DATA FROM 00·031
TERMINATE OUTPUT TRANSFER
..--
3} ASSERT DATA TRANSFER AND SIZE ACKNOWLEDGE (DSACKx)
I} NEGATE
AS
AND
iiS
2} REMOVE DATA FROM 00·031
3} NEGATE OBEN
- . .
TERMINATE CYCLE
i
I
I} NEGATE DSACKx
I
START NEXT CYCLE
Figure 7-24. Asynchronous Write Cycle Flowchart
MOTOROLA
MC68030 USER'S MANUAL
7-37