gen_rdm

[hugo]

ein random generator der zufällige werte in festen ezitabständen erzeugt.
die ausgangsamplitude und der offset sowie die Zeitspanne zwischen 2 werten sind programmierbar

FUNCTION_BLOCK gen_rdm
VAR_INPUT
   PT : TIME;
   AM : REAL := 1;
   OS : REAL;
END_VAR
VAR_OUTPUT
   Q : BOOL;
   Out : REAL;
END_VAR
VAR
   tx : TIME;
   last : TIME;
   init : BOOL;
   temp : REAL;
END_VAR

(*
   version 1.0   7 feb 2007
   programmer    oscat
   tested BY      oscat

this signal generator generates a random output. The signal is defined by period time (PT),
amplitude (AM), offset (OS).
The Output waveform will have its max peak at AM/2 + OS and its minimum peak at -AM/2 + OS.
The period time PT defines how often the output signal will jump to a new randow value.
The Output Q will be true for one cycle anytime the output OUT has changed

*)

(* read system time and prepare input data *)
tx := TIME() - last;

(* init section *)
IF NOT init THEN
   init := TRUE;
   last := tx;
   tx := t#0s;
END_IF;

(* add last if one cycle is finished *)
IF tx >= pt THEN
   last := last + pt;
   tx := tx - pt;

   (* generate output signal *)
   out := am * (RDM(0) - 0.5) + os;
   q := TRUE;
ELSE
   q := FALSE;
END_IF;