Browse Prior Art Database

RF SELECT BIT FOR ADDRESSABLE SYSTEMS

IP.com Disclosure Number: IPCOM000008099D
Original Publication Date: 1997-Mar-01
Included in the Prior Art Database: 2002-May-17
Document File: 1 page(s) / 52K

Publishing Venue

Motorola

Related People

John Pigott: AUTHOR

Abstract

One of the dificulties in assembling a system of addressable nodes, such as a multiplexed bus, is the initial assignment of unique addresses to (initially) identical nodes. Because initially the nodes are all programmed at (say) address 00000, then there is no way to distinguish between different units after the bus has been assembled, but no IDS have been programmed. Here is one technique to allow nodes to be distinguished.

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8 MO7OROLA Technical Developments

RF SELECT BIT FOR ADDRESSABLE SYSTEMS

by John Pigott

  One of the dificulties in assembling a system of addressable nodes, such as a multiplexed bus, is the initial assignment of unique addresses to (initially) identical nodes. Because initially the nodes are all programmed at (say) address 00000, then there is no way to distinguish between different units after the bus has been assembled, but no IDS have been programmed. Here is one technique to allow nodes to be distinguished.

  Many inputs in ICs are sensitive to radiated RF. If an input is built with a NPN whose base is con- nected to the pin, and with a resistor between base and emitter, then this junction will rectify RF cou- pled to the pin (possibly through a long PCB trace connected to it, acting as an antenna), and the tran- sistor will turn on. The sensitivity of this can be controlled by the value of the base-emitter resistor. This circuit is not too frequency sensitive. This

NPN can therefore be controlled by holding an RF wand physically close to the node. This can be used in production as a non-contact means of selecting or identifying a particular node.

  The address decoding for the node can be based on the internally stored EPROM and the bit from this RF input (RFSEL bit). One possibnility is that if the EPROM bits are all 'O's (i.e. unprogrammed from the factory), then address decoding uses this additional bit as a selector. However, if any of the EPROM bits are not...