
External Interface Module (EIM)
Freescale Semiconductor
13-7
Figure 13-6. Basic Read Bus Cycle
Note the following characteristics of a basic read:
In S3, data is made available by the external device on the falling edge of CLKOUT and is sampled
on the rising edge of CLKOUT with TA asserted.
In S4, the external device can stop driving data after the rising edge of CLKOUT. However data
could be driven up to S5.
For a read cycle, the external device stops driving data between S4 and S5.
13.4.4
Write Cycle
During a write cycle, the processor sends data to the memory or to a peripheral device. The write cycle
Figure 13-7. Write Cycle Flowchart
R/W
TIP
TS
D[31:0]
TA
Read
S0
S1
S2
S3
S4
S5
CLKOUT
CSn, BSn, OE
A[31:0], SIZ[1:0]
External Device
1.
Set R/W to write
2.
Place address on A[31:0]
3.
Assert TIP and SIZ[1:0]
4.
Assert TS
5.
Place data on D[31:0]
6.
Negate TS
1.
Decode address
2.
Store data on D[31:0]
3.
Assert TA
1.
Sample TA low
2.
Stop driving data from D[31:0]
1.
Negate TA
1.
Start next cycle
ColdFire processor
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3