Intelligent Serial I/O Boards
Thanks to the many built-in communication protocols, the Super
PLCs also make more than great serial-based I/O boards for PCs or
You can use the T100MD's RS232 port for
straightforward connection to a PC. With an RS232-to-RS485 adapter (such as the Auto485) as many as 31 super PLCs can
be connected to a single PC to provide distributed I/Os at up to 4000 ft away.
Click here to
view a sample Visual Basic communication program which is provided to aid
Visual Basic programmers to rapidly learn how to talk to our PLCs using the native
|A T100MD+ not only offers analog I/Os and digital I/Os for the host PC,
you can make use of its local intelligence to obtain special I/Os such as PWM and Stepper Motor outputs, High Speed Encoder, Frequency Measurement or even Interrupt inputs!
The PC can also display messages on local LCD attached to the T100MD+ for a PC to send messages remotely to
the factory floor, for example. These features are simply impossible to find on other
serial-based "dumb" I/O boards.
The T100MD+ supports a few standard communication
protocols as follow:
1) Native ASCII based protocols, e.g.
2) MODBUS ASCII protocol. e.g. ":01030000000102nn"
3) MODBUS RTU protocol (binary based).
4) OMRON C20H protocol (ASCII type).
Our proprietary ASCII based native protocol allows
you to read or write to every I/O and internal variable within the PLC using a rather
straightforward command/response exchange of ASCII strings. Please see the T100MD+ User's Manual Chapter 3
and 4 for detailed description of these protocols. A
The MODUS ASCII and RTU protocols are simple but
popular communication protocols and you can find their documentation at www.modbus.org. The memory
mapping of T100MD PLC to the MODBUS registers can be found in Chapter 5 of the T100MD+ User's Manual.
In addition, you can even implement
your own proprietary communication protocol using the powerful TBASIC
language! This allows a T100MD+ to be used with an obscure host computer that must use a
certain fixed, proprietary serial protocol to control external I/Os.
Every T100MD+ PLC has built-in TBASIC commands (such as
NETCMD$, READMODBUS, WRITEMODBUS) for communicating with another PLCs or 3rd party MODBUS
devices. Hence it is possible for one or more T100MD+ to be used as slave I/O boards for a
master T100MD+ PLC. This makes it possible to use more analog or special I/Os than are
available on a standard T100MD+ PLC for complex control tasks.
Example, in the arrangement shown below
the master PLC could have access to 24 analog I/Os, 6
PWMs, 6 stepper controllers and 6 encoder inputs!
By using RS485-to-Fiber Optics converters, you can
use the M-series PLCs as remote I/O boards via Optical Fiber! This allows the
communication cable to be laid across open field where lightning risk can cause
severe damage to copper wire based communication links. On request by a customer we tested
one such converter made by R.E. Smith (www.rs485.com, model FC485) as shown in the
The plan is to have a master PLC collect data from
the 20 plus slave PLCs in the plant floor and the data will become available to the
corporate intranet for real-time production reporting and analysis via the corporate
Intranet. However, the customer requires that the master PLC be housed in the
enterprise server room to acquire data from the 20 slave PLCs on the plant floor. The
server room and the plant are in two separate buildings with a car park in between and the
company is located in a tornado country with multiple lightning strikes every year.
Optical fiber is the only feasible means of communication. We tested the above setup and
it works flawlessly and the customer now has a reliable, standalone master PLC
automatically collect production data and delivered to the management via the web browser.
*MODBUS is a registered trademark of Groupe Schneider. OMRON
is a registered trademark of OMRON Corporation.