/FC First Check Bit (Status Word, Bit 0)
The /FC bit signal state controls a logic operation string.
The /FC bit is status word bit 0.
Each logic operation queries the /FC bit signal state and the
addressed contact.
If the /FC bit signal state equals ‘’1,’’ an instruction
logically combines the result of its signal state check on its
addressed contact with the RLO generated since the first check
and stores the result in the RLO bit.
If the /FC bit signal state equals ‘’0,’’ the logic string
begins with a first check.
The logic string ends and the /FC bit is set to ‘’0’’ with
the assignment of a value (S,R,=) or with a RLO-dependent jump instruction.