t
WC
(m)
Strobe
Setup
Hold
t
WR
(m)
t
WP
(m)
t
AW
(m)
t
DS
(m)
t
DH
(m)
EMA_CS[n]
EMA_A[x:0]
EMA_BA[1:0]
EMA_WE
EMA_D[x:0]
W_SETUP
)
W_STROBE
)
W_HOLD
w
t
WC
(m)
t
cyc
*
3
W_HOLD
w
max
ǒ
t
WR
(m)
t
cyc
,
t
DH
(m)
t
cyc
Ǔ
*
1
W W_STROBE
≥
max
t
AW
(m)
t
cyc
,
t
DS
(m)
t
cyc
- 2
(
)
W_STROBE
w
t
WP
(m)
t
cyc
*
1
Example Configuration
883
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
External Memory Interface A (EMIFA)
shows an asynchronous write access and describes how the EMIFA and ASRAM AC timing
requirements work together to define values for W_SETUP, W_STROBE, and W_HOLD.
From
, the following equations may be derived. t
cyc
is the period at which the EMIFA operates.
The W_SETUP, W_STROBE, and W_HOLD fields are programmed in terms of EMIFA 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
CE
n
CFG is programmed in terms of EMIFA clock cycles, minus 1 cycle. For example, W_SETUP is equal
to W_SETUP width in EMIFA clock cycles minus 1 cycle.
≥
Figure 19-24. Timing Waveform of an ASRAM Write