Quick Help
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. |