Map number simply tells you where you're at on the list of register maps. Click "next" and "prev" to scroll through the list. To advance directly to a specific map, enter the desired number in the "Map #" box, then click Update.

For each remote register to be read, enter the register type, format, number, and slave address or unit number. Size is only applicable when format is Character String, and specifies the number of characters that are to be packed 2 per register. Any size greater than 2 characters implies a multiple register read from the Modbus slave. For coils or discrete inputs, use INT-16 or UINT-16 for register format - in this case, format only affects formatting of local register data.

When the remote register is read, data may be manipulated before being written to the local register. If a bit mask is entered (in hexadecimal), and the remote register type is signed or unsigned (16-bit data), the mask will be bit-wise logical AND-ed with the data, and the retained bits will be right justified in the result. The result will then be multiplied by the scale factor. The offset is then added and this final result is written to the local register number given. The name is optional and used only for display purposes.

The default value will be stored into the local register after the given number of read failures if the fail count is non-zero. Setting the count to zero will disable the default, and the register will retain the most recent value obtained.

The periodic poll time determines how often the remote register will be read. This number, if nonzero, will override the default poll time given in the Devices page for the remote device being read.

You have the option of enabling this map only when a selected register contains a given value. Any local register may be used as the index register. As the name implies, you could have the same local register contain different values based on different maps as indexed by the index register.

Delete will remove the map number shown in the "Map #" box. Insert will insert a new map before the map number shown, and is used for placing maps between existing maps. It is not necessary to use Insert to add maps to the bottom of the list or to define any map presently having zero for a source register or "none" for remote type.

Selecting "none" for remote type effectively deletes the map even though it will still appear in the list until deleted. Unused maps at the end of the list will always show none as the type. If you wish to prevent these from being displayed, reduce the number of maps enabled.

The number of maps enabled simply limits the scope of map review so that you do not have to review a lot of unused maps. If the displayed maps are used up and you need more, increase the enabled number.