Omega Engineering RS-422/485 Technical Description, Features, Modem Control Signal Considerations

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Technical Description

Technical Description

The OMG-ULTRA-COMM422utilizes the 16550 UART. This chip features programmable baud rates, data format, interrupt control and a 16-byte input and output FIFO. Also available as options are the Startech 16C650 and the Texas Instruments 16C750 UARTs, that provide deeper FIFOs (32 bytes) and enhanced clocking features.

A second version of the OMG-ULTRA-COMM422, p/n 3441 is available without the auto enable feature for a reduced price. If point to point RS-422 or RTS enabled RS-485 operations are desired, this option should be considered.

Features

Automatic RS-485 driver enable/disable allows card to appear to be RS-232 requiring no additional drivers

‘PAL’ option allows for unique OEM address selection

‘Shareable’ IRQs allow more than one port to share a single IRQ

IRQs 2/9-7, 10, 11, 12, 15 supported

16550 buffered UARTs standard, 16650 and 16750 UARTS available

16 Bit address decode allows for easier integration

Speeds up to 460.8 K bps available

Multiple clocking modes insuring compatibility with existing software products

Modem Control Signal Considerations

Some software packages require the use of the modem handshake signals such as RTS or CTS. Refer to your application software manual to determine the requirements for modem control signals. If no requirements are mentioned, a safe configuration is to tie RTS to CTS. This configuration will typically satisfy the modem control signal requirements for most communications software.

OMG-ULTRA-COMM422

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Contents User’sGuide Benelux CanadaMexico Czech RepublicContents Figures Overview Factory Default SettingsIntroduction What’s IncludedCard Setup Switch PortAddress Selection Switch Settings Address lines à Address Selected Port # Connector Location Address Example Base=2E0Jumper Selections IRQ SelectionJ1A Interrupt ModesRS-485 Enable Modes Interface Mode Examples J1D J4D Headers J1D- J4D, RS-422Headers J1D- J4D, RS-485 ‘RTS’ Enabled, with ‘No Echo’ Line Termination Name FunctionClock Modes DIV4 DIV2Baud Rates and Divisors for the ‘Div1’ mode For this Data Rate Choose this Data RateFor this Data Rate Choose this Divisor Baud Rates and Divisors for the ‘Div2’ mode Installation Operating System Installation For Windows UsersOther Operating Systems Features Modem Control Signal ConsiderationsTechnical Description Interrupts Why use an ISP? Signal Name Pin # Mode Connector Pin Assignments DB-9 Pin AssignmentsDB-37 Connector Pin Assignments Port #Specifications Appendix a Troubleshooting OMG-ULTRA-COMM422 Appendix B How To Get Assistance Appendix C Electrical Interface RS-422RS-485 Asynchronous Communications Bit Diagram Appendix D Asynchronous CommunicationsAppendix E Silk-Screen Appendix F Compliance Notices WARRANTY/DISCLAIMER Temperature

RS-422/485 specifications

Omega Engineering is a renowned leader in the field of measurement and control technologies, particularly in the realm of data communication for industrial automation. The RS-422 and RS-485 protocols are part of Omega's robust offering, designed to facilitate reliable and efficient data transmission over relatively long distances. These protocols are widely used in various applications ranging from industrial machinery to building automation systems.

One of the main features of RS-422 is its ability to support long-distance communication, allowing data to be transmitted up to 4,000 feet (approximately 1,200 meters) at speeds of up to 10 Mbps. This is achieved through the use of differential signaling, which provides improved noise immunity compared to single-ended signaling systems. RS-422 employs a single transmitter and multiple receivers, making it ideal for point-to-multipoint configurations.

On the other hand, RS-485 extends the capabilities of RS-422 by allowing multiple devices to be connected on the same bus. It supports up to 32 devices, which can be either transmitters or receivers, making it exceptionally versatile for networking applications. RS-485 can communicate effectively over distances up to 4,000 feet and at speeds of 10 Mbps as well. This makes it an attractive option for applications where several devices need to communicate with a central controller.

An essential characteristic of both protocols is their resilience to electromagnetic interference, which is often a concern in industrial environments. The differential signaling used in RS-422 and RS-485 reduces noise susceptibility, ensuring data integrity even in challenging conditions. Additionally, these protocols function effectively in half-duplex or full-duplex modes, providing flexibility based on application requirements.

Moreover, Omega Engineering’s implementations of RS-422 and RS-485 comply with established standards, ensuring compatibility with a wide range of devices. This interoperability is crucial for seamless integration into existing systems and enhancing overall productivity.

In summary, Omega Engineering's RS-422 and RS-485 technologies offer robust, reliable, and versatile solutions for data communication in industrial settings. With features such as long-distance communication, multiple device connections, and exceptional noise immunity, these protocols continue to serve as foundational technologies in various automation and control applications. As industries evolve, Omega Engineering remains committed to advancing these technologies to meet the growing demands of modern data communication.