Datasheet

AD7822/AD7825/AD7829
Rev. C | Page 19 of 28
AD7822 STANDALONE OPERATION
The AD7822, being the single channel device, does not have any
multiplexer addressing associated with it and can be controlled
with just one signal, that is, the
CONVST
signal. As shown in
Figure 31, the
RD
and
CS
pins are both tied to the
EOC
pin.
The resulting signal can be used as an interrupt request signal
(IRQ) on a DSP, as a
WR
signal to memory, or as a CLK to a
latch or ASIC. The timing for this interface, as shown in
Figure 31,
demonstrates how, with the
CONVST
signal alone, a conversion
can be initiated, data is latched out, and the operating mode of
the AD7822 can be selected.
AD7825/
AD7829
A0
A1
A2
CS
RD
DB7 TO DB0
CS
RD
DB0 TO DB7
A15 TO A3
A2 TO A0
ADC I/O ADDRESS
MUX ADDRESS
A/D RESULT
MUX ADDRESS
(CHANNEL SELECTION A0 TO A2)
LATCHED
MICROPROCESSOR READ CYCLE
ADDRESS
DECODE
SYSTEM BUS
01321-031
A15 TO A3
Figure 30. AD7825/AD7829 Simplified Microinterfacing Scheme
CONVST
RD
CS
EOC
DB7 TO DB0
AD7822
DSP/
LATCH/ASIC
CONVST
EOC
RD
CS
DB0 TO DB7 A/D RESULT
t
1
t
4
01321-032
Figure 31. AD7822 Standalone Operation