1 (****************************************************************

     2 

     3               RTC - Real-time clock

     4 

     5 Q is a copy of IN.

     6 

     7 When IN = FALSE, CDT is the current date and time as set by the

     8 PLC driver.

     9 

    10 When IN changes from FALSE to TRUE, PDT is stored. As long as IN is

    11 TRUE, CDT is equal to PDT + the amount of time since PDT was loaded.

    12 

    13 ****************************************************************)

    14 

    15 FUNCTION_BLOCK RTC

    16    VAR_INPUT

    17      IN : BOOL;                  (* 0 - current time, 1 - load time from 

    18 PDT *)

    19      PDT : DT;                   (* Preset datetime *)

    20    END_VAR

    21    VAR_OUTPUT

    22      Q : BOOL := FALSE;          (* Copy of IN *)

    23      CDT : DT;                   (* Datetime, current or relative to PDT *)

    24    END_VAR

    25 

    26    VAR

    27      PREV_IN : BOOL := FALSE;

    28      OFFSET : TIME;

    29      CURRENT_TIME : DT;

    30    END_VAR

    31 

    32    {__SET_VAR(data__->,CURRENT_TIME,__CURRENT_TIME)}

    33 

    34    IF IN

    35    THEN

    36      IF NOT PREV_IN

    37      THEN

    38          OFFSET := PDT - CURRENT_TIME;

    39      END_IF;

    40 

    41      (* PDT + time since PDT was loaded *)

    42      CDT := CURRENT_TIME + OFFSET;

    43    ELSE

    44      CDT := CURRENT_TIME;

    45    END_IF;

    46 

    47    Q := IN;

    48    PREV_IN := IN;

    49 

    50 END_FUNCTION_BLOCK

    51