MPC555 / MPC556
MEMORY ACCESS TIMING
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
F-2
LEGEND
Shaded areas = address phase ; Non-shaded areas = data phase
Table F-2 Timing Examples
Access
# Clock
Total
1
2
3
4
5
6
7
8
9
10
11
12
13
Load/Store ->
Ebus
L
U
E
6
1
NOTES:
1. N is the number of clocks from external address valid until external data valid in the case of read cycle. In the case
of zero wait states, N = 2.
E
U
L
Load/Store ->
IMB 16 bits
L
U
IMB
6
IMB
U
L
Instruction
Fetch-> cmf
new page
3 concecutive
accesses
C,U
2
U
2
2. Core instruction fetch data bus is usualy the UBUS
C,U
1
U
C,U
1
U
Instruction
Fetch-> cmf
new page
Load/Store ->
IMB
C,U
2
U
L
U
IMB
6
IMB
U
L
Instruction
Fetch-> cmf
new page
Load/Store ->
IMB
C
U
6
U
L
U
IMB
6
IMB
U
L
External Bus->
cmf
new page
E
U
5
U
E
External Bus->
IMB
E
U
IMB
7
IMB
U
E
Instruction
Fetch-> cmf
2 concecutive
accesses &
External Bus->
cmf
C,U
2
U
C
-
3
3. 8 clocks are dedicated for external access, and internal accesses are denied.
-
-
-
-
-
-
-
U
11
U
E
retry
E
4
4. Assuming the external master immediately retries
U
8
U
E
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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