MPC555
/
MPC556
MEMORY CONTROLLER
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
10-14
In
, notice the following:
• Because ACS = 0, TRLX being set does not delay the assertion of the CS and
WE strobes.
• Because CSNT = 1, WE/BE is negated one clock cycle earlier than normal. (Refer
).
• CS is not negated one clock cycle earlier, since ACS = 00.
• The total cycle length is three clock cycles, determined as follows:
— The basic memory cycle requires two clock cycles.
— One extra clock cycle is required due to the effect of TRLX on the negation of
the WE/BE strobes.
Figure 10-12 Relaxed Timing – Write Access
(ACS = 00, SCY = 0, CSNT = 1, TRLX = 1
10.3.4 Extended Hold Time on Read Accesses
For devices that require a long disconnection time from the data bus on read access-
es, the bit EHTR in the corresponding OR register can be set. In this case any MPC555
/ MPC556 access to the external bus following a read access to the referred memory
bank is delayed by one clock cycle unless it is a read access to the same bank.
CLOCK
Address
TS
TA
CS
RD/WR
WE/BE
Data
OE
CSNT = 1
No Effect, ACS = 00
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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