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  • Create an RS-485 Serial Device Network

    RS485 NetworksThe 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, the NBS-10 was the first card developed for that product family. It marks more than twenty years of Cimetrics support for its 9-bit customers, and represents Cimetrics continued commitment to legacy support.

    RS485 networks are everywhere (still).

    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 from the first 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.