
External Memory Controller (EMC)
Symphony DSP56724/DSP56725 Multi-Core Audio Processors, Rev. 0
Freescale Semiconductor
21-81
21.4.4.6
Extended Hold Time on Read Accesses
Slow memory devices that take a long time to turn off their data bus drivers on read accesses should choose
some non-zero combination of ORx[TRLX] and ORx[EHTR]. The next accesses after a read access to a
slow memory device is delayed by the number of clock cycles (specified in the ORx register), in addition
to any existing bus turnaround cycle.
21.4.4.7
Memory System Interface Example Using UPM
Connecting the external memory UPM controller to a DRAM device requires a detailed examination of
the timing diagrams representing the possible memory cycles that must be performed when accessing this
device. This section describes timing diagrams for various UPM configurations, using fast-page mode
DRAM as an example, with CRR[CLKDIV] = 4 or 8.
The examples shown are for illustrative purposes only, and may not represent the timing necessary for any
specific device used with the EMC. In the examples, LGPL1 is programmed to drive R/W of the DRAM,
although any LGPLx signal may be used for this purpose.