The input variables of this function block are typically the output variables of another function block whose status is to be reported. Upon the occurrence of an event at the REQ input, the values of these input variables are translated into a WSTRING output in the format of a service primitive as defined in IEC 61499-1. For instance, the inputs
ENAME="CNF", Q=true, STATUS="OK", DATA="Received Data"
would be translated into the output string
"CNF+(OK,Received Data)".

The operation of this function block is defined by the following algorithm.

ALGORITHM REQ IN Java :
  PRIM.value = ENAME.value
    + (Q.value ? "+(" : "-(")
    + STATUS.value + ','
    + DATA.value + ')';
END_ALGORITHM