Automatic restoring circuit for groove signals of contactless card

Abstract

The invention discloses an automatic restoring circuit for groove signals of a contactless card. The automatic restoring circuit comprises an RF (radio frequency) module, an N-bit counter, a preset value module, a comparer and a data latch, wherein the RF module is used for receiving radio frequency signals and restoring clock signals which include data information; the N-bit counter is used for counting low-level duration time of the groove signals outputted by the RF module; the preset value module is used for presetting a maximum tolerable low-level duration time value of the groove signals; the comparer is used for comparing an output value of the counter with the preset value, and outputting a marking signal when the output value is equal to the preset value; and the data latch is used for sampling the marking signal outputted by the comparer, obtaining the marking signal at the output end Q of the comparer and enabling the RF module to restore by the aid of the marking signal so as to enable the groove signals to restore to the correct high level. The groove signals can restore to the correct high level to enable subsequent communication to be proceeded normally when the groove signals are overlength.

Description

technical field [0001] The invention relates to the field of non-contact cards, in particular to a non-contact card groove signal automatic recovery circuit. Background technique [0002] Data transmission systems are well known and widely used to exchange information and conduct transactions with remotely located portable data devices. Said portable data device is usually called a card, smart card or tag. Likewise, data sending systems are often referred to as card readers. The transaction begins when the card enters the energizing zone of the reader. Specifically, a card reader (terminal) generates a power signal and a data signal (information signal), and transmits the data signal using a carrier signal. Detection and reception of the carrier signal remotely powers the card and enables the card to perform its intended function. [0003] Remotely powered (ie, contactless) data devices (ie, cards) can be used to perform a variety of tasks, including theft prevention, pe...

AI Technical Summary

Problems solved by technology

In this way, if the RF (radio frequency) demodulation circuit is compatible with two types of interfaces, in typeA mode, it is likely to cause misadjustment due to changes in the signal amplitude on the antenna, such as sudden changes in field strength, or when multiple cards are anti-collision. It may cause the RF demodulation circuit to mistakenly treat it as a normal signal for demodulation, resulting in subsequent communication errors, or even failure to communicate normally

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