Prosoft-technology MVI46-MCM Manual de usuario descargar pdf (Pagina 67)

MVI46-MCM ♦ SLC Platform Reference

Modbus Communication Module User Manual

ProSoft Technology, Inc. Page 67 of 108

March 29, 2011

Slaves are defined to the system when the module initializes the master

command list. Each slave defined will be set to a state of one in this initial step. If

the master port fails to communicate with a slave device (retry count expired on a

command), the master will set the state of the slave to a value of 2 in the status

table. This suspends communication with the slave device for a user specified

scan count (ErrorDelayCntr value in the MCMPort object for each port). Each

time a command in the list is scanned that has the address of a suspended

slave, the delay counter value will be decremented. When the value reaches

zero, the slave state will be set to one. This will enable polling of the slave.

Block ID Description

3002 Request for first 128 slave status values for Modbus Port 1

3003 Request for last 128 slave status values for Modbus Port 1

3102 Request for first 128 slave status values for Modbus Port 2

3103 Request for last 128 slave status values for Modbus Port 2

Block Request from Processor to Module

Word Offset Description Length

0 3002 to 3003 or 3102 to 3103 1

1 to 247 Spare 246

The module will recognize the request by receiving the special write block code

and respond with a read block with the following format.

Block Response from Module to Processor

Word Offset Description Length

0 Reserved 1

1 Write Block ID 1

2 to 129 Slave Poll Status Data 128

130 to 248 Spare 119

249 3002 to 3003 or 3102 to 3103 1

Ladder logic can be written to override the value in the slave status table to

disable slaves (state value of 3) by sending a special block of data from the

processor to the slave. Port 1 slaves are disabled using block 3000, and Port 2

slaves are disabled using block 3100. Each block contains the slave node

addresses to disable.

1 2 ... 62 63 64 65 66 67 68 69 70 71 72 ... 107 108

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Prosoft-technology MVI46-MCM Manual de usuario Pagina 67