Is this a Modbus register question?
We have cheap HMI. Proface 5800 SP model. When making tags in HMI to map in the HIMA controller.
Modbus is Modbus regardless of whether it's Ethernet or serial (yes they use different encapsulations, but the core Modbus packet remains the same). The need to add or subtract 1from a register address is due to different register numbering conventions used by the equipment vendors. So if you need to add or subtract 1 for Ethernet, you will also need to for serial, when using the same equipment.In ethernet you shift the register by 1. How about serial?
I think you mean 32-bit or 16-bit. Whether a Modbus registers should be interpreted as 32-bit or 16-bit will depend on the data type of the parameter/tag/etc. that is mapped to the Modbus register.HMI is 32 bytes or 16 bytes signal?