SR_FF_FB: Set flip-flop (SR flip-flop)
The SR_FF_FB (FB406) block is used to set or reset the bit of a specified operand based on the signal state of the inputs [S] and [R]. The current signal state of the operand is transferred to output [Q] where it can be queried.
Functionality
Input [S] takes priority over input [R]. This means that when [S] is 1 (True), the signal state of [Q] will always be set to 1 (True) regardless of [R]. If [S] is 0 (False) and [R] is 1 (True), [Q] will be reset to 0 (False).
If both S and R are 0 (False) the instruction is not performed and the operand remains unchanged.
Function table
Inputs | Outputs | ||
S | R | Q | QN (inverse) |
1 (True) | 0 (False) | 1 (True) | 0 (False) |
0 (False) | 1 (True) | 0 (False) | 1 (True) |
1 (True) | 1 (True) | 1 (True) | 0 (False) |
0 (False) | 0 (False) | Last state (no change) | Last state (no change) |
Inputs
Pin | E | Description |
S | pa | Set |
R | pa | Reset |
Outputs
Pin | E | Description |
Q | a | Output |
QN | a | Inverse output |
Input values
Pin | Description | Data Type | Default value | E.g. Engineering unit or Text group | Min. | Max. |
S | Set | Boolean | 0 (False) | False, True |
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R | Reset | Boolean | 0 (False) | False, True |
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Output values
Pin | Description | Data Type | Default value | E.g. Engineering unit or Text group | Min. | Max. |
Q | Output | Boolean | 0 (False) | False, True |
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QN | Inverse output | Boolean | 1 (True) | False, True |
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Process response
Standard (see General rules and information).
Troubleshooting
Standard (see General rules and information).