ProSoft Technology MVI71-MNET - Manual (Page 71)

Reference MVI71-MNET ♦ PLC Platform
User Manual Modbus TCP/IP Interface Module
ProSoft Technology, Inc.
Page 71 of 109
June 23, 2009
The parameters passed with the block construct the command. The IP Address
for the node to reach on the network is entered in four registers (1 to 4). Each
digit of the IP address is entered an the appropriate register. For example, to
interface with node 192.168.0.100, enter the values 192, 168, 0 and 100 in
registers 1 to 4. The Service Port field selects the TCP service port on the
server to connect. If the parameter is set to 502, a standard MBAP message will
be generated. All other service port values will generate a Modbus command
message encapsulated in a TCP/IP packet.
The Internal DB Address parameter specifies the module’s database location to
associate with the command. The Point Count parameter defines the number of
points or registers for the command. The Swap Code is used with Modbus
functions 3 and 4 requests to change the word or byte order. The Modbus
Function Code has one of the following values 1, 2, 3, 4, 5, 6, 15 or 16. The
Device Database Address is the Modbus register or point in the remote slave
device to be associated with the command. When the module receives the block,
it will process it and place it in the command queue.
The module will respond to each command block with a read block. The following
table describes the format of this block.
Offset Description Length
50 0 1
51 2000 1
52 Write Block ID 1
53 0=Fail, 1=Success 1
Word two of the block can be used by the ladder logic to determine if the
command was added to the command queue of the module. The command will
only fail if the command queue for the port is full (100 commands for each
queue).
Command Control
Command control blocks place commands in the command list into the
command queue. The client has a command queue of up to 100 commands. The
module services commands in the queue before the user defined command list.
This gives high priority to commands in the queue. Commands placed in the
queue through this mechanism must be defined in the module's command list.
Under normal command list execution, the module will only execute commands
with the Enable parameter set to one or two. If the value is set to zero, the
command is skipped. Commands may be placed in the command queue with an
Enable parameter set to zero using this feature.
These commands can then be executed using the command control blocks.
One to six commands can be placed in the command queue with a single
request. The following table describes the format for this block.
Offset Description Length
50 5001 to 5006 1
51 Command index 1