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1
Setup
2
Strobe
3
Hold
4
EM_CS
EM_CS (ASRAM)
EM_A[21:0]/
EM_BA[1:0]
EM_A[21:0]/
EM_BA[1:0] (ASRAM)
EM_OE
EM_OE (ASRAM)
EM_D[15:0]
EM_D[15:0]
(ASRAM)
t
CS
t
CS
t
RC
(m)
t
EM_A
t
EM_A
t
EM_OE
t
EM_OE
t
SU
t
EM_D
t
ACC
(m)
t
EM_D
t
OH
(m)
t
H
t
COD
(m)
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Use Cases
Figure 14. Timing Waveform of an ASRAM Read with PCB Delays
From Figure 15, the following equations may be derived. t
cyc
is the period at which the EMIF operates. The
W_SETUP, W_STROBE, and W_HOLD fields are programmed in terms of EMIF cycles where as the data
sheet specifications are typically given is nano seconds. This is explains the presence of t
cyc
in the
denominator of the following equations. A minus 1 is included in the equations because each field in
ACFGn is programmed in terms of EMIF clock cycles, minus 1 cycle. For example, W_SETUP is equal to
W_SETUP width in EMIF clock cycles minus 1 cycle.
35
SPRUEQ7C–February 2010 Asynchronous External Memory Interface (EMIF)
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