Register number indicates which register is being configured on this page. This register number would also be the Modbus holding register number you would request from a Modbus master if the ValuPoint is functioning as a slave. Click "next" and "prev" to scroll through the register list. To advance directly to a specific register, enter the desired number in the "Register #" box, then click Update.

Links, if any, are links to read and write maps in one of the clients that are mapped to this register. Click on the link to see the client read or write rule.

Select the data format you wish to assign to this register from the data format list. This selection will determine whether one, two, or more consecutive Modbus registers will be consumed by the data value that starts at this register number. Modbus protocol specifies that a "register" is always strictly 16 bits. Therefore a 64-bit number will occupy 4 consecutive "registers" that is treated as one data value by a typical application. If data format is character, then you also need to specify a size in number of characters. Characters will be packed 2 ASCII characters per Modbus register. Therefore, as an example, a 20-character string will occupy 10 Modbus "registers".

Enter any arbitrary name for this register. It is used only for display purposes, and is not accessible via Modbus.

Modbus protocol does not dictate whether the low order or high order data comes first when data greater than 16 bits is represented by multiple registers. To make sure the ValuPoint is compatible with other devices, you have the option of reversing the order with the check box after the comment "Least significant data should be in first register". If left unchecked, then the most significant data will be in the first register (also referred to as "big endian").

Check "Display as hexadecimal" if you wish to view data as a string of hexadecimal digits. This is most useful when a register is a collection of bits that each have a specific meaning.

The "Is Persistent" option means this register will retain its most recent value through a power outage, with time delay restrictions as noted in the user guide. The persistent selection does not take effect until the Reset Persistent button is clicked on the Resources page.

A default value can be applied to this register immediately at power-up and/or if not updated by a remote source within the specified amount of time. The remote source will typically be a remote Modbus master.

You can also use the timeout and default to indicate when there has been a communication failure and the ValuPoint is acting as a slave. An example of flagging a fault would be to force "room temperature" to -99 if communications timed out. This obviously wrong value would tell you that communications are broken. Without this obvious flag value, a seemingly good data value might be displayed while being hours or even days old and no longer valid.