Dallas Semiconductor Corporation

Donald R Diaz

Robert D Lee

Michael L Bolan

Hal Kurkowski

Stephen M Curry

Francis A Scherpenberg

Kevin E Deierling

Kevin E Peirling

A system architecture which provides efficient data communication, over a one-wire bus, with a portable data module which does not necessarily include any accurate time base whatsoever. The time base in the module can be extremely crude (e.g. more than 4:1 uncertainty). An open-collector architecture is used, with electrical relations defined to absolutely minimize the drain on the portable module's battery. The protocol has been specified so that the module never sources current to the data line, but only sinks current. The protocol includes signals for read; write-zero; write-one; and reset. Each one-bit transaction is initiated by a falling edge from the host. The time base in the module defines a delay, after which (in write mode) the module tests the data state of the data line. In read mode, after a falling edge the module does or does not turn on its pull-down transistor, depending on the data value. Thus, the host system, after the falling edge, attempts to pull the data line high again, and then tests the potential of the data line to ascertain the data value.

Single wire data communication method

A secured metal token using a single wire communication system is employed to dispense units of value and to provide a secure storage device for controlling the dispensing of articles or service items. The metal token can be formed of two pieces with a simplified electronic circuit inside which can contain units of value for the dispensing of items using the memory within the metal token as a secure vault. The token uses a simple two wire (ground and combined clock/data) arrangment. As goods are purchased or services rendered the value of those good or services is deducted from a prestored amount within the token.

Metal token having units of value stored therein using a single wire

A communication circuit is provided in which reads from a device are controlled by sensing a transition by a host communicating with a device. The device then accepts a one which holds the line high for a predetermined time period or accepts a zero when the line is held high for a different time period. The sending of data is accomplished in a symmetrical relationship by having the device after the host pulls the line high by either by allowing the line to remain high or forcing the line to ground within the requisite time periods. This allows the 'slave' device to consume almost no power in either the read or the write modes.

Single wire communication system

An electronic token has at least two conductive surfaces which form either in total or in part a crush resistant casing in which a semiconductor memory is placed. Coupled to the two conductive surfaces is a set of input logic which is used to detect whether or not the first conductive surface is coupled to a device in which a first voltage or a second voltage is present and in which data can be stored in the semiconductor memory accordingly. Output logic is also provided so as to selectively poll the first conductive surface of said casing towards the second voltage with the output logic being electronically coupled to the semiconductor memory so that data may be retrieved from the stored memory. The stored information may be used for controlling access to items, for example as a lock. It may further be used as an inventory control device, postage control device, currency device for the sale of goods. This item can act as a portable storage device which allows through its updating capabilities a mechanism for updating values within the device, such as money units or their equivalents.

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Carrollton, TX, United States of America

Donald R Diaz