Half-Duplex SIM I/O Level Shifter to Prevent Data Feedback
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Solution Overview
Problem
Existing interface circuits for SIM card communication are complex, require significant space, and cause packet latencies due to the need for decoders, level shifters, and encoders to manage voltage differences between mobile devices and SIM cards, leading to inefficient half-duplex communication.
Innovation Solution
A bidirectional autonomous level shifter with a controller and delay elements that selectively enables transmitters based on packet flow direction, preventing concurrent operation to maintain half-duplex communication and reduce complexity by using separate voltage supplies for receivers and transmitters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing interface circuits with decoders, level shifters, and encoders are used to manage voltage differences, then voltage level compatibility is achieved, but device complexity and IC space requirements increase significantly
Solution Approach 1:
The patent combines the decoder, level shifter, and encoder functions into a single integrated I/O level shifter circuit. This merging eliminates the need for separate discrete components while maintaining voltage level compatibility between mobile devices and SIM cards, directly reducing device complexity and IC space requirements.
Solution Approach 2:
The I/O level shifter is designed as a multi-functional circuit that simultaneously performs decoding, voltage level shifting, and encoding operations. This universal circuit handles both voltage adaptation and data signal processing, replacing multiple specialized components with a single versatile unit.
2Adaptability or versatility
If existing interface circuits with multiple components are used, then voltage level compatibility is achieved, but packet latency increases
Solution Approach 1:
By integrating the decoder, level shifter, and encoder into a single circuit block, the patent eliminates the sequential processing delays that occur when data passes through separate components. The combined circuit processes signals in a single pass, reducing packet latency while maintaining voltage compatibility.
3Productivity
If transmitters are operated concurrently in half-duplex communication, then data transmission capability is maintained, but positive data feedback occurs
Solution Approach 1:
The controller monitors the communication state and uses feedback signals to determine when to enable or disable transmitters. By detecting the direction of packet flow and responding to communication state changes, the controller prevents concurrent transmitter operation that would cause positive data feedback, while maintaining full data transmission capability through proper timing control.
Data Source
AI summary
An input/output (I/O) level shifter for a subscriber identification module (SIM) interface includes a controller configured to apply a first enable signal to turn ON a first transmitter when the direction of packet flow is from an interface device to a SIM card, and is configured to apply a second enable signal to turn ON a second transmitter when the direction of packet flow is from the SIM card to the interface device. The controller is configured to not apply the first and the second enable signals concurrently. The controller selectively controls the ON/OFF period of the first and the second transmitter to maintain half-duplex communication on the interface I/O line and the SIM I/O line to prevent undesired positive data feedback.