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MPC555
/
MPC556
MEMORY CONTROLLER
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
10-10
10.3.3 Relaxed Timing Examples
The TRLX field is provided for memory systems that need a more relaxed timing be-
tween signals. When TRLX is set and ACS = 0b00, the memory controller inserts an
additional cycle between address and strobes (CS line and WE/OE).
When TRLX and CSNT are both set in a write to memory, the strobe lines (WE/BE[0:3]
and CS, if ACS = 0b00) are negated one clock earlier than in the regular case.
Note that in the case of a bank selected to work with external transfer acknowledge
(SETA = 1) and TRLX = 1, the memory controller does not support external devices
providing TA to complete the transfer with zero wait states. The minimum access du-
ration in this case equals three clock cycles.
shows a read access with relaxed timing. Note the following:
• Strobes (OE and CS) assertion time is delayed one clock relative to address
(TRLX bit set effect).
• Strobe (CS) is further delayed (half-clock) relative to address due to ACS field be-
ing set to 11.
• Total cycle length = 5, is determined as follows:
— Two clocks for basic cycle
— SCY = 1 determines 1 wait state, which is multiplied by two due to TRLX being
set.
— Extra clock is added due to TRLX effect on the strobes.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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