F
3-
-0
4A
D
S
4-
C
h.
Is
ol
at
ed
A
na
lo
g
In
.
3--8
F3--04ADS 4-Channel Isolated Analog Input
Module Operation
Before you begin writing the control program, it is important to take a few minutes to
understand how the module processes and represents the analog signals.
The F3--04ADS module supplies1 channel of data per each CPU scan. Since there
are four channels, it can take up to four scans to get data for all channels. Once all
channels have been scanned the process starts over with channel 1.
You do not have to select all of the channels. Unused channels are not processed, so
if you select only two channels, then each channel will be updated every other scan.
Channel 1
Scan N
Read the data
Store data
I/O Update
Execute Application Program
Channel 2
Scan N+1
Channel 3
Scan N+2
Channel 4
Scan N+3
Channel 1
Scan N+4
Scan
Even though the channel updates to the CPU are synchronous with the CPU scan,
the module asynchronously monitors the analog transmitter signal and converts the
signal to a 12-bit binary representation. This enables the module to continuously
provide accurate measurements without slowing down the discrete control logic in
the RLL program.
Channel Scanning
Sequence
