Method and apparatus for a multiplexed contact between electrical devices

摘要

A method and apparatus for multiplexing an electrical contact interface between two electrical devices uses a time differentiated enablement of two or more different circuit elements in a first electrical device that are accessed via the multiplexed contact by a second electrical device. A timing control circuit in the first electrical device enables and disables circuit elements in the first electrical device coupled to a shared information contact over time. The second electrical device interacts with a first circuit element during an initial period upon connection to the first electrical device, and then interacts with a second circuit element after the initial period.

主权项

1. An electrical device, comprising:
a power contact and an information contact; a memory element coupled between the power contact and the information contact; a sensor circuit coupled in series with a first switch element between the power contact and the information contact; a presence indication circuit coupled in series with a second switch element between the power contact and the information contact; anda timed switch control circuit responsive to an application of a voltage between the power contact and the information contact that maintains the second switch element closed and the first switch element open initially upon the application of the voltage, and after a period of time after the application of the voltage opens the second switch element and closes the first switch element, wherein the timed switch control circuit comprises:
a pair of voltage divider resistors coupled in series between the power contact and the information contact; a timing capacitor coupled in parallel with one of voltage divider resistors; a control switch element having an input responsive to a voltage across the timing capacitor, the control switch element further coupled in series with a control resistance between the power contact and the information contact forming a control node, the control node further coupled to an input of each of the first and second switch elements.