Datasheet

AD5383 Data Sheet
Rev. C | Page 36 of 40
UTILIZING THE FIFO
The AD5383 FIFO mode optimizes total system update rates in
applications where a large number of channels need to be
updated. FIFO mode is only available when parallel interface
mode is selected. The FIFO EN pin is used to enable the FIFO.
The status of FIFO EN is sampled during the initialization
sequence. Therefore, the FIFO status can only be changed by
resetting the device. In a telescope that provides for the cancel-
lation of atmospheric distortion, for example, a large number of
channels need to be updated in a short period of time. In such
systems, as many as 320 channels need to be updated within
25 µs to 30 µs. 320 channels require the use of 10 AD5383s.
With FIFO mode enabled, the data write cycle time is 40 ns;
therefore, each group consisting of 32 channels can be fully
loaded in 1.28 µs. In FIFO mode, a complete group of 32
channels updates in 11.5 µs. The time taken to update all 320
channels is 11.5 µs + 9 × 1.28 µs = 23 µs. Figure 44 shows the
FIFO operation scheme.
GROUP A
CHNLS 0-31
GROUP B
CHNLS 32-63
GROUP C
CHNLS
64-95
GROUP D
CHNLS
96-127
GROUP E
CHNLS
128-159
GROUP F
CHNLS
160-191
GROUP G
CHNLS
192-223
GROUP H
CHNLS
224-255
GROUP I
CHNLS
256-287
GROUP J
CHNLS
288-319
TIME TO UPDATE 320 CHANNELS = 23µs
1.28µs
11.5µs
11.5µs
1.28µs
FIFO DATA LOAD
GROUP A
FIFO DATA LOAD
GROUP B
OUTPUT UPDATE
TIME FOR GROUP A
1.28µs
11.5µs
FIFO DATA LOAD
GROUP J
OUTPUT UPDATE
TIME FOR GROUP J
OUTPUT UPDATE
TIME FOR GROUP B
03734-044
Figure 44. Using FIFO Mode 320 Channels Updated in Under 25 µs