Product manual

TAC Xenta Server – Gateway, Technical Manual B Protocols
Schneider Electric Buildings AB, June 2011 143 (184)
04-00124-06-en
Register or Holding Register). The first number in the Register
Number will not be used for identifying the register type.
• Register Table
– If Full Address range is used, select the table
type Discrete Input, Coil, Input Register or Holding Register in
this column. If Fixed Address Blocks is used, all types have to be
set to Fixed Address Blocks.
• Register Data Type
– Selects the format of the value within the
slave’s memory. Most register values are 16-bit signed or unsigned
integers, or 1 bit switch/coil status flags. But two registers can be
combined into one 32-bit integer or floating-point value. And in
some cases 2, 3 or 4 registers are combined into a single integer
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
Note
• It is not possible to mix Fixed Address Blocks register table type
with Full Address Range register table types in the same device
template.