mcf5307cft90b Freescale Semiconductor, Inc, mcf5307cft90b Datasheet - Page 395

• Manufacturer Part Number: mcf5307cft90b
• Description: Mcf5307 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

18.4.3 Read Cycle
During a read cycle, the MCF5307 receives data from memory or from a peripheral device.
Figure 18-5 is a read cycle flowchart.
The read cycle timing diagram is shown in Figure 18-6.
S5
State
S5
Read
Write
1.
2.
3.
4.
5.
6.
1.
1.
Set R/W to read
Place address on A[31:0]
Assert TT[1:0], TM[2:0], TIP,
and SIZ[1:0]
Assert TS
Assert AS
Negate TS
Sample TA low and latch data
Start next cycle
Cycle
An external device has at most two BCLKO cycles after the
start of S4 to three-state the data bus after data is sampled in S3.
This applies to basic read cycles, fast-termination cycles, and
the last transfer of a burst.
In the following timing diagrams, TA waveforms apply for chip
selects programmed to enable either internal or external
termination. TA assertion should look the same in either case.
MCF5307
Low
BCLKO
Table 18-4. Bus Cycle States (Continued)
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Figure 18-5. Read Cycle Flowchart
AS, CS, BE/BWE, and OE are negated on the BCLKO falling edge. The
MCF5307 stops driving address lines and R/W on the rising edge of BCLKO,
terminating the read or write cycle. At the same time, the MCF5307 negates
TT[1:0], TM[2:0], TIP, and SIZ[1:0] on the rising edge of BCLKO.
Note that the rising edge of BCLKO may be the start of S0 for the next access
cycle; in this case, TIP remains asserted and R/W may not transition,
depending on the nature of the back-to-back cycles.
The external device stops driving data between S4 and S5.
The data bus returns to high impedance on the rising edge of BCLKO. The
rising edge of BCLKO may be the start of S0 for the next access.
Chapter 18. Bus Operation
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NOTE:
NOTE:
Description
1.
2.
3.
1.
2.
Decode address and select the
appropriate slave device.
Drive data on D[31:0]
Assert TA
Negate TA.
Stop driving D[31:0]
System
Data Transfer Operation
18-7