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98640A Analog Input Interface
2) Request a series of readings with an assembly language routine.
3) Set the EPCON line low. The analog-to-digital
con~ersion
for the first reading will start in ap-
proximately 3 microseconds.
4) Set the IPACDA line low. This must happen 1 to 15 microseconds after you set EPCON low.
5) Hold EPCON and IPACDA low until all of the requested readings have been taken.
Figure
4'-1
shows a simple circuit that can be used to bring IPACDA Iowan appropriate amount of
time after EPCON goes low. This circuit uses the +5 volt power supply from terminal 28 of the wire
termination assembly.
WIRE TERMINATION
ASSEMBLY RECPTICALES
t29
EXTERNAL PACE INPUT
(EPCON)
1N 914
.J
~
TYPICAL
0
OPEN TO
......
START
7
30
READING
INTERNAL PACE DISABLE
(lPACDA)
100 PF
-~
I
• 28
+5V
Figure 4-1. IPACDA timing circuit for externally paced burst readings
Combinations. You can combine the above two methods of external pacing if your application
requires. We won't go into those combinations here; we leave that as an exercise for the interested
reader. The methods above should give you enough information to make your combination work.
4-12
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