Modbus DRO

[Romanr9999]

I´m working in a resin dispensing machine that uses Mach3 and has  a PLC to control some machine functions.
One functions the PLC controls is a variable speed resin pump. I need to control the pump speed from within a Mach3 screen.
The idea is to have a DRO in the screen with the pump RPM and be able to send this value to the PLC via modbus. The RPM value should be a discrete value going from 1 to 100.

I understand how to use modbus for bit signals (like a sensor on-off status) but I don´t get how to use it for discrete values.

Any leads to point me in the right direction would be greately appreciated.
Thanks.

[poppabear]

since your using output values, use OUTPUT HOLDING on the serial plugin modbus set up (note it will be a integer).
then in brian, map your DRO99 through a formula A*100 then to you serial plugin modbus config, local var as your termination.

scott