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Rockwell Automation 1746-XXXX SLC 500 4-Channel Analog I/O Modules User Manual User Manual

Page 50

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Publication 1746-UM005B-EN-P - June 2004

4-12 Module Operation and System Considerations

which exceed low and high limits respectively. For this example, the
analog input value is in word 1 of slot 1 (I1:1.1). Whenever the input
value exceeds a limit, this program latches a binary variable in
memory that could serve as an alarm indication at some other point in
the program.

The second program is for SLC 5/02 processors. This program uses the
Limit Test instruction that checks both low and high limits in a single
instruction. This instruction assumes that the analog input value is in
word 1 of slot 1 (I1:1.1).

As in the above program, whenever the input value exceeds a limit,
this program latches a binary variable in memory which could serve as
an alarm indication at some other point in the program.

GREATER THAN
Source A I1:1.1
Source B 16,384

LESS THAN
Source A I1:1.1
Source B 0

GRT

B3/0

(L)

B3/0

(L)

B3/0

(U)

END

Remainder of Program

Turn OFF

Alarm

Turn ON Alarm, Low Limit

Exceeded

Turn ON Alarm, High Limit

Exceeded

LES

LIM

B3/0

(L)

B3/0

(U)

END

Remainder of Program

Turn OFF

Alarm

Turn ON Alarm,

Limit Exceeded

LIMIT TEST (CIRC)
Low Lim 16,385
Test I1:1.1
High Lim ±1