Motorola ColdFire MCF5281 - Manual (Page 231)

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.
States are described in Table 13-3 .
13.4.4 Write Cycle
During a write cycle, the processor sends data to the memory or to a peripheral device. The write cycle
flowchart is shown in
Figure 13-7 .
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