IC Card Signal Initiation via Short Pulse
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Solution Overview
Problem
Microcircuit cards conforming to the ISO 7816-3 standard cannot initiate communication with external devices due to potential collisions when trying to signal their willingness to communicate, leading to misinterpretation or non-receipt of commands.
Innovation Solution
A microcircuit card sends a signal of duration strictly less than the shortest significant information unit during a communication line's silence to indicate its desire to communicate, allowing detection even in collisions, and includes means to retransmit the signal if the line is busy, with specific embodiments using the I/O line or RST contact line to prevent misinterpretation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the microcircuit card places the I/O line in a predetermined state to indicate communication willingness, then the card can initiate communication, but collision may occur when the external device simultaneously places the line in the same state
Solution Approach 1:
The patent changes the temporal parameter of the signal by using a pulse duration strictly less than the minimum duration of significant information defined in the ISO 7816-3 standard. This parameter change allows the card's initiation signal to be distinguishable from normal communication signals, resolving the collision problem while maintaining the ability to initiate communication
2Reliability
If the microcircuit card uses a signal duration equal to or greater than the minimum significant information duration, then the signal can be clearly transmitted, but it cannot be distinguished from normal communication signals during collision
Solution Approach 1:
The patent modifies the duration parameter of the communication signal to be strictly less than the minimum duration of significant information (Tmin) defined in the ISO 7816-3 standard. This creates a distinct temporal signature that prevents misinterpretation during collision events, as the external device can detect pulses shorter than Tmin as initiation signals rather than valid data
3Reliability
If the microcircuit card waits for external device initiation, then communication protocol compliance is maintained, but the card cannot proactively initiate communication
Solution Approach 1:
The patent implements preliminary action by having the card place the I/O line in a predetermined state (logic level 0) for a brief duration before normal communication begins. This preliminary signal serves as an initiation request that the external device can recognize and respond to, allowing the card to proactively start communication while ultimately following the master/slave protocol
Solution Approach 2:
The patent uses the I/O line as an intermediary signal channel during the initialization phase. By temporarily using this line to convey initiation intent through a distinctive short pulse, the card can signal its communication willingness without violating the standardized protocol structure for actual data transmission
Data Source
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Figure 5
AI summary
The card (40) has a microprocessor (10) and a communication interface (30) for sending a signal to an external device over a communication line e.g. input/output line (I/O) and a reset line (RST), during silent window, to indicate communication of the card with the device, to the device. Duration of the signal is less than that of shorter significant information to be emitted by the device on the line along a protocol standardized between the card and the device. The card conforms to ISO 7816standard, and the input/output line conforms to ISO 7816-3standard. An independent claim is also included for a method for assuring communication of a chip card to an external device.