Modicon M580 PLC - Comparing DateTime

How do you go about implementing, on the M580 PLC, how many days, hours, minutes before a predefine event in the future?

The RRTC_DT yields the PLC datetime stamp in Datetime (DT ) format. Doing a DT_TO_ARINT type conversion gives the PLC datetime stamp (DT format) to an Integer Array of 4 elements with date and time in BCD format.

Example:
If the input is:
DT_Variable = dt#2006-05-11-10:46:16
Then the output is:
DateAndTime_ARRAY[1] = 16#1600
DateAndTime_ARRAY[2] = 16#1046
DateAndTime_ARRAY[3] = 16#0511
DateAndTime_ARRAY[4] = 16#2006

But dealing with arrays is tedious. Does anyone know a quick way to perform an excel equivalent DATEDIFF function on M580 PLC?

Also, the old 984 PLCs used to have a STAT word to check the health status of the various drops. Is there something similar on the M580?

SUB? I'm pretty sure you just subtract one from the other and it gives you a TIME (duration) as a result.

Yup - you are correct! Upon further investigation, Modicon has a SUB_DT_DT function that compares to two DT values and outputs their difference in TIME format.

Ok, next question....is there a equivalence for the old STAT function.
How do i detect changes to the hardware (field devices, hardware changes, etc)

modiconguy said:

SUB? I'm pretty sure you just subtract one from the other and it gives you a TIME (duration) as a result.

Click to expand...

You need to look healt bits (CRA/RIO) from DDT data type for IO rack or device health bits.