Utilizing Modbus Function 23 with AC500 controller

I am trying to communicate with an ABB ACS880 via Ethernet. The ASC880 is furnished with a FENA-11 communications module which supports Modbus/TCP Function 17h. The processor being util;ized is a PM563-R-ETH-AC. The problem lies in utilizing the structure ETH_MOD_FCT23_TYPE with ETH_MOD_MAST. I am hoping for an example of the variable declaration and code required. The desired result is to write 15 words (ACS880_Out[1..15]) to 400001 and read 15 words (ASC880_In[1..15]) from 400051.