Chapter 8 Logic Instructions 
8-15 
 
FB/FC 
FB  SR is used for giving priority to the Set input. 
 
  Parameters 
Meaning 
Description  Valid range   
SET 
Input 
SET signal  TRUE or FALSE 
Reset 
signal 
Reset signal  TRUE or FALSE 
Q 
signal 
Output  Output signal  TRUE or FALSE 
 
 
Boolean 
Bit string  Integer 
Real 
number 
Time, date 
String 
BYTE 
DWORD 
USINT 
UINT 
UDINT 
ULINT 
SINT 
INT 
LINT 
LREAL 
TIME 
DATE 
TOD 
STRING 
SET 
● 
                                     
Reset 
● 
                                     
Q 
● 
                                     
Note: 
The symbol ● indicates that the parameter is allowed to connect to the variable or constant of the data 
type. 
  Function Explanation 
When the SET and Reset inputs of RS are both TRUE, SET is given the priority. 
   
SR
EN ENO
SET
Q
SR_instance
Q
Reset