Sending negative values to Omron E5CN

[RoTaTech]

I have 24 E5CN controllers hooked up RS485 to a Omron CJ.

They communicate using the Compoway/F protocol, and a routine written with the PCMR instructions to format data to send the PV to the controllers, and read both SV and PV.

I can READ positive or negative values from the controller; they are stored as single signed integers.

I can not seem to send a negative setpoint to the controllers.
The value sits in memory as a single word signed integer, but the SV on the controller will not change. If I go to the controller and punch in a negative setpoint, it will accept it, and I can read it properly in the PLC.

Any ideas? I've p-ssed away best part of a day trying to make it work.

 

[iant]

Check the symbol setup - you may be using an integer - it may need to be setup as signed or maybe real

 

[gtsuport]

In the Adjustment menu, have you turned the Communications Writing (CMWt) parameter ON?
Reference Manual H156-E1-03 page 180.
Hope this will help.

 

[RoTaTech]

Found it.

The protocol sends double word signed binary to the controller. When I did my math in single word, and MOVing it to the data area to send, it was stripping off the negative, because bit 15 would be the sign bit; the controller is expecting bit 31 to be the sign.