Asynchronous Interface
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9.6.3
Asynchronous Reads
Figure 9–41 show an asynchronous read with the setup, strobe, and hold param-
eter programmed with the values 2,3, and 1, respectively. An asynchronous read
proceeds as follows:
-
At the beginning of the setup period:
J
CE becomes active.
J
AOE becomes active.
J
BE[3:0] becomes valid.
J
EA becomes valid.
-
At the beginning of a strobe period, ARE becomes active
-
At the beginning of a hold period:
J
ARE becomes inactive (high).
J
Data is sampled on the CLKOUT1 on the ECLKOUT rising edge con-
current with the beginning of the hold period (the end of the strobe pe-
riod) and just prior to the ARE low-to-high transition.
-
At the end of the hold period: AOE becomes inactive as long as another
read access to the same CE space is not scheduled for the next cycle.
-
For the ’C6201/C6202/C6701, CE stays active for seven minus the value
of Read Hold cycles after the last access (DMA transfer or CPU access).
For example, if read HOLD = 1, then CE stays active for six more cycles.
This does not affect performance and merely reflects the EMIF’s over-
head.
-
For the ’C6211/C6711, the CEn signal goes high just after the pro-
grammed hold period.