This Function Block type utilizes the Execution Control Chart (ECC) shown above and the algorithms listed below for a skeleton implementation of the generic REQUESTER Service Interface Function Block (SIFB) type shown in Figure 20a of IEC 61499-1.

• The OUT variable reports the state transitions preceding the most recent output event occurrence.
• Subclasses of this type can re-define the algorithms and I/O variable definitions as necessary.

ALGORITHM INIT IN ST :
QO := TRUE;
STATUS := "OK";
OUT := "INIT=>RUNNING";
END_ALGORITHM

ALGORITHM REQ IN ST :
QO := TRUE;
STATUS := "OK";
OUT := "REQ=>RUNNING";
END_ALGORITHM

ALGORITHM TERMINATE IN ST :
QO := FALSE;
STATUS := "TERMINATED";
OUT := "TERMINATING=>TERMINATED";
END_ALGORITHM

ALGORITHM INH IN ST : (* REQ inhibited *)
QO := FALSE;
STATUS := "INHIBITED";
OUT := "INH=>RUNNING";