Modbus data question.

Good Day All,
I'm stuck with this "minor" data issue, please help.
I'd like to display engine hours data on HMI and SCADA system. I've a PROSOFT MV146-MCM card with SLC 5/05 controller. LOgic had been written before to collect Data from CAT Engine EMCP through Modbus and everything worked fine untl recently when the engine hours displayed were incorrect.
The rawdata engine hours on N32:64 is now a -ve number. CAT says this the engine hours data is in 2 registers of 4Bytes each( i'm assuming N32:63 and N32:64)and that the resolution is 0.05hour/bit.
I'm struggling on how to use this information to correctly display the engine running hours.
I've recycled power to the PLC hoping to clear a corrupt regista=er but i keep getting the same -ve number.
I've attached the some logic for reference. Please help.

The problem is that the Hours counter is 32-bit Unsigned integer.

The SLC-500 platform Integers are 16-bit Signed integers. The most-significant bit (bit 15) is the Sign; 0 for positive, 1 for negative.

Once the accumulated time got above 2^15, the highest bit was interpreted by the SLC-500 as a Sign bit, which is why the number now appears negative.

32768 counts of 0.05 hours each is about 68 days of runtime. Does that sound about correct ?

The SLC-5/05 doesn't have a Long datatype or an Unsigned data type, but most SCADA systems can treat two adjacent 16-bit Integers as an Unsigned or Long datatype.

Your other option will be to manually convert this Integer to a floating-point value in the controller. There are a handful of options for this, but let's take a look at the SCADA system first.

Thanks Ken You really made my day. Yes the theres been abot 68 days of run time. Thanks again.

I'm using PanelView 32 for HMI and RSView 32 for SCADA and am not sure how to make them display the correct hours.

Hi,

Maybe, read one register, multiply it by 65535 then add the second register to the result. Or reverse, depending on the word order.

Make sure the result can handle the 32 bit number.