Symphony DSP56724/DSP56725 Multi-Core Audio Processors, Rev. 0
21-76
Freescale Semiconductor
External Memory Controller (EMC)
The following sections provide additional information about some of the RAM word fields.
21.4.4.4.2
Chip-Select Signal Timing (CST
n)
If BRx[MSEL] of the accessed bank selects a UPM on the currently requested cycle, the UPM manipulates
the LCSx signal for that bank with the timing specified in the UPM RAM word CSTn fields. The selected
UPM affects only the assertion and negation of the appropriate LCSx signal.
The state of the selected LCSx signal of the corresponding bank depends on the value of each CSTn bit.
shows how UPMs control LCSx signals.
Figure 21-41. LCSx Signal Selection
1
TODT
Turn-on disable timer. The disable timer associated with each UPM allows a minimum time to be
guaranteed between two successive accesses to the same memory bank. This feature is critical when
DRAM requires a RAS precharge time. TODT turns the timer on to prevent another UPM access to the
same bank until the timer expires.
The disable timer period is determined in MxMR[DSx]. The disable timer does not affect memory
accesses to different banks. Note that TODT must be set together with LAST, otherwise it is ignored.
0 The disable timer is turned off.
1 The disable timer for the current bank is activated, preventing a new access to the same bank (when
controlled by the UPMs) until the disable timer expires. For example, a precharge time.
0
LAST
Last word. When LAST is read in a RAM word, the current UPM pattern terminates and the control signal
timing set in the RAM word is applied to the current (and last) cycle. However, if the disable timer is
activated and the next access is to the same bank, the execution of the next UPM pattern is held off and
the control signal values specified in the last word are extended in duration for the number of clock cycles
specified in MxMR[DSx].
0 The UPM continues executing RAM words.
1 Indicates the last RAM word in the program. The service to the UPM request is done after this cycle
concludes.
Table 21-72. RAM Word Field Descriptions (Continued)
Bits
Name
Description
UPMA/B/C
SDRAM
GPCM
MUX
BRx[MSEL]
LCS3
LCS4
LCS5
LCS6
LCS7
Switch
Bank Selected
LCS0
LCS1
LCS2
Содержание Symphony DSP56724
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