A1042 - 9-Bit Networking

Create an RS-485 Serial Device Network

RS485 Networks The Cimetrics 9-bit products allow networking of serial devices - usually microcontrollers used in process instrumentation.

For those who have been using Cimetrics 9-bit NBS products for years, this is the latest incarnation of support for that series. It marks twenty years of Cimetrics support for its 9-bit customers, and represents Cimetrics continued commitment to legacy support.

RS485 networks are everywhere (still).
http://en.wikipedia.org/wiki/EIA-485

Many users are not so much familiar with RS485 as the protocols which travel over this datalink. These protocols include Modbus RTU, BACnet MS/TP, ARCNET RS485, Johnson N2, Siemens P1, and Profibus.

Some protocols make use of some UARTs' capabilities to manipulate the 9th bit in a character frame to allow these "9-bit" characters to be a special part of the signaling in the protocol. This is related to the use/concept of parity in character transmission. One can think of 9-bit signaling as toggling, character by character, between mark and space versions of stuck parity.

Cimetrics itself, in the 1990s, developed a 9-bit protocol called the "NBS" or Nine Bit Solution. The NBS used the characters with the 9th bit set as node address signaling channel. This method is excellent for small and resource constrained microprocessors which need to communicate in small groups with each other - like on process industry equipment - Cimetrics main market for NBS.

Over the years, Cimetrics has provided many NBS cards to support the Nine Bit Solution and other 9-bit protocols. This card is the latest generation of Cimetrics NBS-x cards which support 9-bit signaling, whatever the 9-bit use may be.

Cimetrics NBS-x cards support most all common forms of RS485 signaling well. And can be used for protocols including Modbus RTU, BACnet MS/TP, ARCNET RS485, Johnson N2, Siemens P1, and Profibus.

NBS-42L PCI to RS485 Interface Card

The NBS-42L are PCI-bus RS-485 asynchronous serial communication interface cards for PCs. Based on an Oxford 16C950 UART similar to Intel’s 82510 UART, the NBS-42L have several features particularly suited to RS-485 multi-drop networking. Some of their special features are as follows:

support for the 9-bit character format commonly used in microcontroller networks
speeds of up to 250,000 bits/second
built-in ESD protection reduces failures
slew-rate limited RS-485 transceiver reduces RFI and cable termination problems
hardware can automatically perform transmit/receive switching
jumper selected RS-485 bus termination and biasing

These products are designed for RS-485 and simplex RS-422 networks (and NOT 4-wire RS-485 or 4-wire RS-422 networks).

The NBS-42L are not appropriate for data communication systems that use synchronous serial communication protocols such as HDLC, SDLC and Bitbus. Likewise, Manchester Encoding is not supported by the NBS-42L.

NBS-42L PCI to RS485 Network Interface Card - Specification

Specifications PCI to RS485 Network Interface Card - Specification

Electrical Interface: slew-rate limited, unit impedance load
Ports: One
Connectors: DB-9 female with adapter to 3-pin “Phoenix”
UART: Oxford 16C950 UART compatible with Intel P82510
Data Rate: up to 250,000 bits/second (limited by the RS-485 transceiver)
PCI Bus Interface: 3.3 volt, 32 bit, PCI rev. 2.2 compliant
Operating Temperature Range: 0 to 70 C
Power Consumption: 400 mA typical at 3.3 volts (from the PCI bus)
Dimensions: 123 mm (length) by 60 mm (height) (excluding PCI bracket)
Regulatory Approvals: USA: Class B digital device
Canada: Class B digital apparatus

Documentation for A1042 NBS-42L 9-bit RS-485 Card

Documentation for NBS42L