
Symphony DSP56724/DSP56725 Multi-Core Audio Processors, Rev. 0
21-68
Freescale Semiconductor
External Memory Controller (EMC)
21.4.4.1.1
Memory Access Requests
The user must ensure that the UPM is appropriately initialized before a request occurs.
The UPM supports two types of memory reads and writes:
•
A single-beat transfer transfers one operand consisting of up to a single word. A single-beat cycle
starts with one transfer start and ends with one transfer acknowledge.
•
A burst transfer transfers exactly four double words. The burst cycle starts with one transfer start
but ends after eight transfer acknowledges.
Ensure that patterns for single-beat transfers contain one and only one transfer acknowledge (UTA bit in
RAM word set high). For a burst transfer, the patterns must contain the exact number of transfer
acknowledges required.
Any transfers that do not naturally fit single or burst transfers are synthesized as a series of single transfers.
These accesses are treated by the UPM as back-to-back, single-beat transfers. Burst transfers can also be
inhibited by setting ORx[BI]. Burst performance can be achieved by ensuring that UPM transactions are
8-word aligned with a transaction size being some multiple of 8-word, which is a natural fit for a cache-line
transfer.
21.4.4.1.2
UPM Refresh Timer Requests
Each UPM contains a refresh timer that can be programmed to generate refresh service requests of a
particular pattern in the RAM array.
shows the clock division hardware associated with
memory refresh timer request generation. The UPM refresh timer register (URT) defines the period for the
timers associated with all three UPMs.
Figure 21-36. Memory Refresh Timer Request Block Diagram
By default, all external memory refreshes are performed using the refresh pattern of UPMA. This means
that if refresh is required, MAMR[RFEN] must be set (1). It also means that only one refresh routine
should be programmed and be placed in UPMA, which serves as the refresh executor. Any banks assigned
Table 21-71. UPM Routines Start Addresses
UPM Routine
Routine Start
Address
Read single-beat (RSS)
0x00
Read burst (RBS)
0x08
Write single-beat (WSS)
0x18
Write burst (WBS)
0x20
Refresh timer (RTS)
0x30
Exception condition (EXS)
0x3C
UPM refresh timer request
System
Divide by URT
PTP Prescaling
Clock