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Digital Input/Output Event Synchronization System Disclosure Number: IPCOM000030962D
Original Publication Date: 2004-Sep-02
Included in the Prior Art Database: 2004-Sep-02
Document File: 4 page(s) / 76K

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This article details a method and system for driving digital Input/Output (IO) signals in synchronization with specific events. In the proposed implementation, digital direction control signals are synchronized to a PWM synthesized sine wave such that direction control changes only occur at zero volt crossings to mitigate electrical disturbances.

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Digital Input/Output Event Synchronization System

This invention is a software abstraction of the digital IO registers in a microprocessor. Traditionally, software would write to a IO port directly, however, there is little or no way synchronize more than one signal if they are modified in different parts of a program. This invention is intended to be made in software. There may or may not exist hardware analogs of this invention.

    In some motor dive applications three phase AC sinusoids are synthesized in real-time. We ideally need to synchronize these outputs with other outputs, such as motor direction control bits. The specific application we are interested in is using a small AC motor (single phase) on the three phase drive. It has two coils that are common in one end. We would like to use the 3 phases (one common) to connect to this little motor, but now need a way to switch which phase is active with respect to the common leg. Ideally this selection would be synchronized to the edges of PWM signals as to allow decay of inductive energy storage in the motor to reduce voltage transients. In another implementation, it is feasible to synchronize output pulses such that the synthesized sine wave zero crossings are incident on the change of state of the direction control pins for even greater noise reduction. Consider the following system for controlling a low voltage AC motor with dual direction windings.

    Winding energization is mutually exclusive or motor burns...