DH+ issue

I’m working on a problem where I’m getting a WatchDog error randomly between a PLC 5 DH+ channel and a DataLink DL4500 DH+ to Modbustcp device (Communicates to ABB 800x). The ABB controller has Bit 15 in Word N150:51 set to a 1. Once per scan If I see the bit is ON then I cut it back off and consider everything ok. If N150:51/15 stays off for 10 secs then I’m saying there is a Comms issue. Having said that I start doing some digging in the PLC 5 and see sometimes the N150:51/15 bit won’t come of for 6 to 8 secs, sometimes it’s less than a second. This lead me to putting my frontline Netdecoder software to work and found something I can’t explain. The DL4500 Device is doing a Write command for N150:51 4 words long when you look at the data parse out word 1 of the write has a value of 249 then sometimes is has a value of (33017) How can a integer be 33017 in a PLC 5?? I have some more work to do because my understanding was the ABB Conntroller was set up to always have a one in data point for N150:51/15. That doesn't seem to be the case with it sending a value of 249, But i dont know what the 33107 is at a 16 bit word. Any ideas???See screen shots

Just spitballing - 16 bit max value of an Unsigned INT is 65k but in a Signed INT the range is -32K to +32K the high order bit being the sign bit.
It looks like FTE is treating it as unsigned ?
Its no coincidence that 33017-249=32767

My guess is that FTE is displaying values as un-signed 16-bit integers, even though their parser ought to know that the PLC-5 uses only signed 16-bit integers where Bit 15 is the sign bit. The fact that it's a Binary (B) data type file instead of an Integer (N) data type file might be why that mistake is made.

sometimes the N150:51/15 bit won’t come of for 6 to 8 secs, sometimes it’s less than a second

Click to expand...

That bit is the difference between those values:

33017 = 0x80F9 = 1000 0000 1111 1001
249 = 0x00F9 = 0000 0000 1111 1001

TheWaterboy said:

It looks like FTE is treating it as unsigned ?
Its no coincidence that 33017-249=32768

Click to expand...

This seems right. Breaking the two down into binary we see that 33017 = 1000000011111001 while 249 = 0000000011111001, meaning bit 15 is changing.