ProSoft Technology 5202-DFNT-MCM4 - Manual (Page 15)

Functional Overview MCM ♦ ProLinx Gateway
Driver Manual Modbus Master/Slave
ProSoft Technology, Inc.
Page 15 of 80
October 16, 2009
2.4.1 Modbus Port Access to Database
The Modbus slave support in the gateway permits remote Master applications
(that is, HMI software, Quantum processors, and so on) to read from and write to
the gateway’s database.
When configured as a slave, the internal database of the MCM gateway is used
as the source for read requests and the destination for write requests from
remote Masters. Access to the database is controlled by the command type
received in the incoming message from the remote Master. The following table
defines the relationship of the gateway’s internal database to the addresses
required in the incoming Modbus TCP/IP requests:
Database Address Modbus Address
0 40001 (five-digit addressing) or 400001 (six-digit addressing)
1000 41001 or 410001
2000 42001 or 420001
3000 43001 or 430001
3999 44000 or 440000
The following virtual addresses are not part of the normal gateway user database
and are not valid addresses for standard data. However, these addresses may
be used for incoming commands that are requesting 32-bit floating-point data. To
use addresses in this upper range requires you to:
1 Set the Float Flag (page 19) to Y ES
2 Set the Float Start (page 19) to a database address in the range below
3 Set the Float Offset (page 20) to a database address in the gateway user
memory area shown above.
Remember that, once you do this, all data in addresses above the Float Offset
address will be treated as 32-bit floating-point data and require two gateway
memory registers per Modbus address.
Database Address Modbus Address
4000 44001 (five-digit addressing) or 440001 (six-digit addressing)
5000 45001 or 450001
6000 46001or 460001
7000 47001 or 470001
8000 48001 or 480001
9000 49001or 490001
9999 50000 or 500000