sys_iRingCounter

Group

Data type

INT

Name

Ring counter 2.5ms

The data register acts as a ring counter. The register value is increased by one every 2.5ms (counting range: 0–32767 and -32768–0). Compare the register values (v) at two different times (v1 and v2) to determine the elapsed time (t): t = (v2-v1) x 2.5ms.

The register value is updated at the beginning of each scan.

Example

if (NOT bIsInitialized) then
    bIsInitialized:=TRUE;
    iRingCounter_Old:=sys_iRingCounter_2ms5;
    iScans:=1;
else
    iRingCounter_New:=sys_iRingCounter_2ms5;
    iRingCounterDiff:=iRingCounter_New-iRingCounter_Old;        
    if (iRingCounterDiff>0) then (* Important to work also for shorter scan times *)
        diScanTime_µs:=(INT_TO_DINT(iRingCounterDiff)*2500)/INT_TO_DINT(iScans);
        iRingCounter_Old:=iRingCounter_New;
        iScans:=1;
    else
        iScans:=iScans+1; 
    end_if;
end_if;