
MOTOROLA
Chapter 10. Memory Controller
10-15
Chip-Select Timing
10.3.3 Relaxed Timing Examples
The TRLX field is provided for memory systems that need a more relaxed timing between
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
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 that provide TA to
complete the transfer with zero wait states. The minimum
access duration in this case equals three clock cycles.
Figure 10-11 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 being
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 (2 + (SCY x 2)).
— Extra clock is added due to TRLX effect on the strobes.