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September, 2002: SoftPLC now also provides a Modbus RTU Slave protocol
driver, in addition to the rich communications protocol set already supported by
this open architecture controller (which includes TCP/IP ethernet, Data Highway,
A-B DF1 serial, Modbus Master, and more). The driver is now included with all
SoftPLC systems at no cost.
This new Modbus Slave driver makes it easy for SoftPLC users to interface to
even more products such as Distributed Control Systems (DCS) and SCADA
systems. Up to 8 serial ports are supported for slave connections to multiple
Modbus Master systems/devices. Over 1 million tags can be defined in a single
SoftPLC controller.
Example applications for SoftPLC utilizing the Modbus Slave driver include:
- Process or machine control applications where the PLC (SoftPLC) needs to
interface to a DCS or SCADA system over Modbus.
- Replace an obsolete proprietary controller (such as an Allen-Bradley PLC-3 or
PLC-5) with SoftPLC, leaving the original DCS and/or SCADA system
programming intact. Automatic ladder logic control code conversion is available
for Allen-Bradley PLC models and customers can elect to use the existing I/O
and/or replace it with another brand, including SoftPLC In Tealware.
- SoftPLC can be used as a data concentrator to multiple HMI/SCADA systems
using the 8 serial ports concurrently. The concentrated data can then be
transferred over ethernet via an in-plant intranet or the internet to another system
for analysis, reporting, etc. using SoftPLC s ability to interact with standard
databases, or by having SoftPLC send an email message
with the data
embedded or attached.
- A simple single port protocol solution for simple HMI's that may not support
other SoftPLC protocols.
- SoftPLC can act as a gateway between a Modicon PLC or other Modbus
Master devices to an Allen-Bradley network, such as Data Highway Plus or A-B
Ethernet.
Features of the Modbus Slave Driver include:
- Supports most commonly used Modbus Functions (0x01, 0x02, 0x03, 0x04,
0x05, 0x06, 0x08, 0x0F, 0x10, 0x16)
- Supports up to 8 ports loading only a single driver instance.
- Each port can have its own mapping of: (a) holding registers; (b) input
registers; (c) input states; (d) output coils. A configuration file is dedicated to
each of these 4 Modicon data areas for each port.
- Each port can be assigned its own baudrate, parity, databits, and stopbits.
- Special global options include DEBUG and IOCHECK. DEBUG allows for
additional diagnostic output. IOCHECK allows the user to reduce the turn
around time by having SoftPLC service the Modbus commands more frequently.
- Easy configuration is done via TOPDOC NexGen using a simple text file.
For more information, click here.
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