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