ProSoft Technology MVI69L-MBS - Manual (Page 56)

MVI69L-MBS Configuration MVI69L-MBS ♦ CompactLogix Platform
User Manual Communication Module
Page 56 of 154 ProSoft Technology, Inc.
January 6, 2014
3.2.3 Modbus Port 1 Commands
This section defines the master command list specifications for a Master port.
In order to interface the MVI69L-MBS module with Modbus slave devices, a
command list needs to be created. The commands in the list specify the slave
device to be addressed, the function to be performed (read or write), the data
area in the device to interface with and the registers in the internal database to
be associated with the device data.
The Master command list supports up to 30 commands. The command list is
processed from top (Command #0) to bottom.
Read commands are executed without condition. Write commands can be set to
execute only if the data in the write command changes (Conditional Enable). If
the register data values in the command have not changed since the command
was last issued, the command is not executed. This feature can be used to
optimize network performance.
The MBS Modbus Master (and Slave) communication drivers support several
data read and write commands. When a command is configured, the type of data
(bit, 16-bit integer, 32-bit float, etc), and the level of Modbus support in the slave
equipment needs to be considered. For information on floating-point support,
please See Floating-Point Support on page 117.
Parameter Value Description
Enable 0 to 4 This field defines whether the command is to be executed
and under what conditions.
Disabled (0) = The command is disabled and is not
executed in the normal polling sequence.
Continuous (1) = The command is executed each scan of
the command list if the Poll Interval (see below) is set to
zero. If the Poll Interval is set to a nonzero value, the
command is executed when the interval timer expires.
Conditional (2) = For write commands only. The command
executes only if the internal data associated with the
command changes.
Bit/Word Override upon Error (3) = For read commands
only. If a command error occurs, the module overrides the
associated database area with the Override Value Upon
Error parameter value.
Float Override upon Error (4) = For read commands only.
If a command error occurs, the module overrides the
associated database area (2x word count) with the Override
Value Upon Error parameter value.
Internal Address 0 to 239 (word-
level)
or
0 to 3839 (bit-
level)
Specifies the module’s internal database register to be
associated with the command. Allowable range is 0 to 239
for Modbus Function Codes 3, 4, 6, or 16, and 0 to 3839 for
Modbus Function Codes 1, 2, 5, or 15.
If the command is a read function, the data read from the
slave device is stored
beginning at the module’s internal
database register value entered in this field. This register
value must lie within the Read Data area of the module’s
memory, defined by the Read Register Start and Read