Normally the only configuration of field device and analyzer Modbus slaves is the the hardware port configuration (baud rate, word size, parity for RTU serial, IP address for ethernet) and a Modbus slave node number for RTU. The registers and word formats are usually defined by the vendor/manufacturer in the register map.
Wireless gateways, PLC controllers and HMI/SCADA typically have a custom configured Modbus slave map, if Modbus slave mode is supported.