Add check bison version in configure.ac file.
To build correctly matiec we need bison greater or equals than 2.4 version.
Now the "configure" script is able to check if system has correctly requirements.
FUNCTION_BLOCK PID
VAR_INPUT
AUTO : BOOL ; (* 0 - manual , 1 - automatic *)
PV : REAL ; (* Process variable *)
SP : REAL ; (* Set point *)
X0 : REAL ; (* Manual output adjustment - *)
(* Typically from transfer station *)
KP : REAL ; (* Proportionality constant *)
TR : REAL ; (* Reset time *)
TD : REAL ; (* Derivative time constant *)
CYCLE : TIME ; (* Sampling period *)
END_VAR
VAR_OUTPUT XOUT : REAL; END_VAR
VAR ERROR : REAL ; (* PV - SP *)
ITERM : INTEGRAL ; (* FB for integral term *)
DTERM : DERIVATIVE ; (* FB for derivative term *)
END_VAR
ERROR := PV - SP ;
(*** Adjust ITERM so that XOUT := X0 when AUTO = 0 ***)
ITERM (RUN := AUTO, R1 := NOT AUTO, XIN := ERROR,
X0 := TR * (X0 - ERROR), CYCLE := CYCLE) ;
DTERM (RUN := AUTO, XIN := ERROR, CYCLE := CYCLE) ;
XOUT := KP * (ERROR + ITERM.XOUT/TR + DTERM.XOUT*TD) ;
END_FUNCTION_BLOCK