Symphony DSP56724/DSP56725 Multi-Core Audio Processors, Rev. 0
21-48
Freescale Semiconductor
External Memory Controller (EMC)
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Simultaneously with the latched memory address. (Refers to the externally latched address and not
the address timing on LAD[23:0]. In other words, the chip select does not assert during LALE).
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One quarter of a clock cycle later (for CRR[CLKDIV] = 4, 8).
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One half of a clock cycle later (for CRR[CLKDIV] = 2, 4, or 8).
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One clock cycle later (for CRR[CLKDIV] = 4), when ORx[XACS] = 1.
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One clock cycle later (for CRR[CLKDIV] = 2), when ORx[XACS] = 1
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Two clock cycles later (for CRR[CLKDIV] = 2, 4, or 8), when ORx[XACS] = 1.
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Three clock cycles later (for CRR[CLKDIV] = 2, 4, or 8), when ORx[XACS] = 1 and
ORx[TRLX] = 1.
The timing diagram in
shows two chip-select assertion timings for the case
CRR[CLKDIV] = 4 or 8. If CRR[CLKDIV] = 2, LCSx asserts identically for ORx[ACS] = 10 or 11.
21.4.2.2.1
Programmable Wait State Configuration
The GPCM supports internal generation of transfer acknowledge. It allows between zero and 30 wait states
to be added to an access by programming ORx[SCY] and ORx[TRLX]. Internal generation of transfer
acknowledge is enabled if ORx[SETA] = 0. If LGTA is asserted externally two bus clock cycles or more
before the wait state counter has expired (to allow for synchronization latency), the current memory cycle
is terminated by LGTA; otherwise the current memory cycle is terminated by the expiration of the wait
state counter. Regardless of the setting of ORx[SETA], wait states prolong the assertion duration of both
LOE and LWEx in the same manner. When TRLX = 1, the number of wait states inserted by the memory
controller is doubled from ORx[SCY] cycles to 2*ORx[SCY] cycles, allowing a maximum of 30 wait
states.
21.4.2.2.2
Chip-Select and Write Enable Negation Timing
shows a basic connection between the EMC and a static memory device. In this case, LCSx is
connected directly to the CE of the memory device. The LWE signal is connected to the WE signals on the
memory device.
Содержание Symphony DSP56724
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