Melsec real-time clock resolution

[goghie]

The program below will measure date and time difference between moment when bMsgSent is ON and bMsgRecieved is ON, and additionally add ms info in wmS_elapsed register:

SET(bMsgSent,bMsgMeasurement);
RST(bMsgRecieved,bMsgMeasurement);
PLS( bMsgMeasurement , bMsgMeasurement_PLS );



DATERD( bMsgMeasurement_PLS , wDateStart );
DATERD( bMsgMeasurement_PLF, wDateStop );

MOVP( bMsgRecieved , w1ms_cnt , wmS_elapsed);
RST(RCPU.stSM.b1sClock AND bMsgMeasurement, w1ms_cnt);


OUTH( (bMsgMeasurement AND NOT T1) , T1 , K1 );
INCP(T1, w1ms_cnt);


PLF( bMsgMeasurement , bMsgMeasurement_PLF );
IF bMsgMeasurement_PLF THEN

wDateDiff[0]:=wDateStop[0]-wDateStart[0];
wDateDiff[1]:=wDateStop[1]-wDateStart[1];
wDateDiff[2]:=wDateStop[2]-wDateStart[2];
wDateDiff[3]:=wDateStop[3]-wDateStart[3];
wDateDiff[4]:=wDateStop[4]-wDateStart[4];
wDateDiff[5]:=ABS(wDateStop[5]-wDateStart[5]);
wDateDiff[6]:=wDateStop[6]-wDateStart[6];
END_IF;

It needs a little of brush up, and it is not bad idea to put it in Fixed Scan with 0.5ms interval.

 

[goghie]

Also not to forget it is important to make following changes in CPU parameters (picture attached)

 

[parky]

Alfredo needs to read ms the DATERD only reads down to seconds, you need to use the SP_DATERD to read the extended time including ms, however, depending on the processor & firmware version only High spec ones can use the SP_DATERD, My processor is an old Q06H so does not support the SP function.
Also a word of caution, try to make the code within the interrupt as small as possible due to the interrupt itteration if the code takes longer than the interrupt time.
Here is a screenshot of a trial where the interrupt ws set at 0.5ms, the PLC scan time is 6.4, the count in the interrupt is 12 or 13 so dividing it by 2 gives 6ms it is +-0.5ms, no point in using decimal places as they cannot be added to the time.