Productivity 3000 modbus communication problem

[Ryan.S]

The 0:00.001 is a valid setting. Lookout will try to poll the device at 0:00.001. But lookout is a windows application, not a real-time software running in real-time OS. Lookout cannot have this fast scan rate. It's not sure how fast it can be, because it depends on how complicated your lookout process is.

[JB_tron]

I have learned more about the failure mode of the Modbus communication.

I was so happy when I got a test program to work, however if I add another expression it kills the communication.

I found that if I put in an expression like Modbus1:300001 it works.

If I add Modbus1:300033 it kills the communication.

If I add Modbus1:300002 (which reads zero) the comm picks up again.

What is the syntax for double word in modbus?

[JB_tron]

The part where I said if I add Modbus1.300033, I have to add the second part Modbus1.300034 or communication will not work.

[Ryan.S]

Try the D300033

[JB_tron]

Yes, that gives me an active number but I don't know what.

The 300001 (near zero), 300033 (near half scale) are counts from 0 to 65535

I suppose I can have data page that has all my my analog inputs thereby keeping the communication structure correct and alive.

Do you know the format this number represents;

[Ryan.S]

The double word register is not a standard register in Modbus specification. Lookout combines two registers and get a DWORD value. The expression is

DWORD value = register1*65536 + register2

So, if 300033 is 1, and 300034 is 2, the D300033 will be 65538

You need to change the Numeric Format of the display on panel to get the exact number, instead of xxE+x

What kind of result do you expect for the DWORD register?