Step 7 F-FB applications in fail-safe PLCs

[larry]

Zuviel Werbung?
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What does the & operation of DB2406.DBX3.7 and M1352.0 accomplish?
The three photos are FB block, fail-safe F-FB block, and FC block, DB2406 is a fail-safe DB block, and the remaining DB block is a normal DB block.

The value of M1301.1 is always 1· , the content of FC115 blocks ends with SET, ensuring that the M1301.1 value is always 1

The problem is that when DB2406.DBX3.7 is 1, then M1352.0 is 1, so M1352.0 is determined by DB2406.DBX3.7 ，If this logic is written, the following & logic should pointless?

 

[Mrtain]

It's a little trick to save space within a network or even an entire network.

Since the eno output will always be true, you simply add an "&" to it.
This takes up less space than if you had placed a single assignment ("=") below the FC.

Not pretty, but useful

 

[larry]

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B2406.DBX3.7- +--------+
+ & +
+ +
+ +
+ +TB1EAF_Stop_OK
M1352.0 - +--------+



Since ENO is set to 1, the value of M1352.0 depends on the value of DB2406.DBX3.7 , so the logic of the '&' operator may not be very useful.

Therefore, by removing the value of DB2406.DBX3.7 and using only M1352.0, the goal can still be achieved.

Is this logical program useful?

It's a little trick to save space within a network or even an entire network.

Since the eno output will always be true, you simply add an "&" to it.
This takes up less space than if you had placed a single assignment ("=") below the FC.

Not pretty, but useful