
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.