Memory card

Abstract

A memory card is provided in which power consumption is reduced by the pull-up resistor of an input terminal and a misoperation induced by the pull-down resistor of a host apparatus is prevented. The memory card has a select terminal connected to the pull-up resistor. When the mode of the memory card is determined based on an input from the select terminal, a relatively low resistance value is selected for the pull-up resistor of the select terminal before a determination timing and the pull-up resistor is restored to an initial resistance value after the mode determination. A relatively high resistance value reduces a leakage current consumed by the pull-up resistor of the select terminal. When a pull-down resistor is connected to the terminal of a memory card host to which the memory card is attached, if the resistance value of the pull-up resistor is excessively high, it is influenced by the drawing in of a current by the pull-down resistor. If the resistance value of the pull-up resistor of the select terminal is lowered at the time of mode determination, an adverse effect of the lowering of a potential by the pull-down resistor can be circumvented.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to a memory card such as Multimedia Card® or to an electronic device. [0002] Multimedia Card® is a kind of a memory card which is embodying a simplified interface and reduced in size and weight. The Multimedia Card has seven connector terminals as external interface terminals. Since a serial interface has been adopted, a load on a host system can be reduced compared with an ATA (AT Attachment) interface adopted by a PC card or a hard disk, which renders the Multimedia Card usable in a simpler and easier system (See Non-Patent Document 1). There is also SD Card® which is another memory card derived from the standards of the Multimedia Card®. The SD Card includes the external terminals of the Multimedia Card, while some types of the Multimedia Card include the command specifications of the SD Card. Of SD Card hosts (host apparatus primarily using the SD Card), there are some which not only use the Multimedia Card as the ...

AI Technical Summary

Benefits of technology

[0008] It is therefore an object of the present invention to provide a memory card and an electronic device in each of which power consumption resulting from the pull-up resistor of an input terminal is reduced and a misoperation induced by the pull-down resistor of a host apparatus is less likely to occur.

[0021] Alternatively, the internal circuit relatively lowers, during a period after a write command until a start bit of data to be written which is supplied to a data terminal as one of the external terminals is detected, an input impedance of the data terminal and returns the input impedance to an initial value after the detection of the start bit. This enhances the reliability of the detection of the leading portion of the data to be written even in the case where the noise immunity of the data input system is low or degraded.

Problems solved by technology

At this time, even a current path resulting from the pull-up resistor of the S card and the pull-down resistor of the S card host is insufficient to hinder the HIGH-level driving by the S card host.

The present inventors have proved that, if the S card host performs a similar recognizing operation with respect to the M card, the pull-down resistor of the S card host draws in a current in the vicinity of the CS terminal of the M card so that a level drop occurs at the CS terminal of the M card, which may result in false mode recognition by the M card.

In an actual situation, however, the M card judges that the CS terminal has been driven to the LOW level due to the drawing in of the current in the vicinity of the CS terminal by the pull-down resistor of the S card host and the resultant potential drop and therefore shits to the SPI mode.

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