Modbus Communication via Siemens CP343-1

I am trying to set up communications between a Siemens CP343-1 module and a DCS. What do the terms client and server mean in the Siemens manual compared to the more traditional master and slave Modbus modes of operation? Also I am not sure how or where to declare the DB's in the MODBUSCP FB. For example, if I want to write data the DCS is looking for bit type values is registers 40001 to 40013 and integer type values in registers 40101 to 401017 how and where do the DB's get declared
Any help is appreciated