REV. B

AD7470/AD7472

–12–

PARALLEL INTERFACE

The parallel interfaces of the AD7470 and AD7472 are 10 bits

and 12 bits wide, respectively. The output data buffers are acti-

vated when both

CS and RD are logic low. At this point, the con-

tents of the data register are placed onto the data bus. Figure 10

shows the timing diagram for the parallel port.

Figure 11 shows the timing diagram for the parallel port when

CS and RD are tied permanently low. In this setup, once BUSY

line goes from high to low, the conversion process is completed.

The data is available on the output bus slightly before the falling

edge of BUSY.

It is important to point out that data bus cannot change state

while the ADC is doing a conversion as this would have a detri-

mental effect on the conversion in progress. The data out lines

will go three-state again when either the

RD or the CS line goes

high. Thus the

CS can be tied low permanently, leaving the RD

for output voltage levels.

BUSY

CS

RD

DBx

CONVST*

*

CONVST SHOULD GO HIGH WHEN THE CLK IS HIGH OR BEFORE THE FIRST CLK CYCLE.

Figure 10. Parallel Port Timing

CONVST*

BUSY

DBx

DATA N

DATA N + 1

*

CONVST SHOULD GO HIGH WHEN THE CLK IS HIGH OR BEFORE THE FIRST CLK CYCLE.

Figure 11. Parallel Port Timing with

CS and RD Tied Low

CLK IN

CONVST

BUSY

CS

RD

Figure 12. Wake-Up Timing Diagram (Burst Clock)