Product manual
TAC Xenta Server – Gateway, Technical Manual B Protocols
Schneider Electric Buildings AB, June 2011 125 (184)
04-00124-06-en
value using the special MOD10k format. The registers can also be
reversed, in these cases they are specified as:
32 bit MOD10k Reverse, 48 bit MOD10k Reverse, or 64 bit
MOD10k Reverse.
• Bit Mask Start and Stop – Allows several signals to be split off
from the applicable N-bit subsets of a single register. The mask
should be left blank to utilize all 16 bits of the register, or the
applicable start and stop bits entered to match the required sub-set
of bits within it. Several different bit masks can be applied to the
same register to monitor different parts of it.
• I/O Signal Direction – Most Modbus Slave device signals are
used to monitor a register’s value, in which case the I/O column
parameter should be set to Read-only (R). In a few cases it may be
necessary to control a coil or holding register’s value, in which
case I/O should be set to Write-only (W).
Setting a coil or holding register’s signal to Read/Write (R/W)
allows both monitoring of its value as well as control of it. How-
ever, this means that the Xenta 913 will continuously read the reg-
ister to fetch the latest value even though it is expecting to have
control of it. This is either a waste of network bandwidth because
the value will not be changed externally, or it presents a potentially
dangerous conflict of control because it can be. In nearly all cases
the Write-only option is preferable because this will cause the
Xenta 913 to read the register’s value once at start-up before it
assumes control of it.
• Coefficient Gain and Offset – Allow the raw register value to be
converted into the desired absolute units. If the raw register value
is a real number then normally no conversion is necessary and the
default gain and offset of 1 and 0 can be used. But if the raw regis-
ter value is an integer then it often needs to have a gain and offset
applied.
As an example, a power meter might generate voltage values as
unsigned integers with the actual voltage multiplied by 10. In this
case the Xenta 913’s gain should be set to 0.1 to convert the raw
units (10*V) into the required absolute units (V).
• Signal DataType – Is set to a default of BOOL, INTEGER or
REAL based on the selected register type. But the default data
type may subsequently need to be changed to suit the applied con-
version coefficient. For example, if a gain of 0.1 is applied to an
Note
•The W and R/W I/O options should only be selected for the reg-
ister types that are described as having read and write capability
in the preceding Register Number table.