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Modbus RTU runs 8051 derivative

Posted: 14 Dec 2004 ?? ?Print Version ?Bookmark and Share

Keywords:microcontroller? mcu? r2 controls? 8051? rtu?

Industrial microcontroller (MCU) supplier R2 Controls now has an 8051-based RTU (Remote Terminal Unit). The company's R301 Modbus Digital RTU is for field and industrial relay-based applications requiring remote configuration, monitoring, and control with a high degree of I/O isolation, as well as high-current output control capabilities.

The module is operable over a slightly extended (at the low end it goes down to -10C) commercial temperature range, and accepts commands conforming to the popular Modbus industrial communications protocol.

Silicon Labs inside

Based on a Silicon Laboratories 8051 SoC microprocessor, the RTU provides a low cost (less than $300) approach for programmable high-speed remote relay control. The Silicon Labs Type C8051F230 8051-type MCU clocks at 22MHz.

The C8051F230 silicon is essentially a 25MIPS mixed-signal chip packing 8KB of in-system programmable flash, 256 bytes of scratchpad RAM, and SPI serial port, a UART, two voltage comparators, and three timers.

Communications capable

Back to the module itself. The R301's communications capabilities ease adaptation into remote industrial or field environments, such as oil and gas distribution systems, water flow monitoring systems, or multiple control points in large industrial complexes.

The RTU features eight optically-isolated digital inputs with pulse counting, two protected digital inputs, and eight Form 1C SPDT relay outputs. Input voltages levels can range from 3V to 40V, AC or DC.

The unit's relay contacts are rated at 10A/120Vac, and include snubber circuit protection. Field wiring is accomplished using 5mm pluggable screw terminal blocks. The I/O is accessed via 56 screw terminals and standard DB9 serial connectors.

The Modbus Digital RTU operates from supply voltages between 9V and 30Vdc. It can be used in a stand-alone mode as a programmable relay controller, or connected via an RS-485 port to other RTUs to create an expanded remote control environment.

- Alex Mendelsohn


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