Method of recognizing a card using a select signal during a determination mode and switching from low to high resistance after the determination
View Patent ↗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.
1. A memory card comprising:
a plurality of external terminals;
an interface unit; and
an erasable and writable nonvolatile memory,
wherein said plurality of external terminals include a select terminal coupled to at least a pair of pull-up resistors including a low resistance value resistor and a high resistance value resistor to provide a pull-up resistance, and
wherein said interface unit switches from said high resistance value resistor to said low resistance value resistor before performing a mode determination for the memory card based on an input from said select terminal during a mode determination period to perform said mode determination using said low resistance value resistor, and switches back to said high resistance value resistor after said mode determination period, and then is capable of starting data input for data storing or data output for data reading from/to a device outside the memory card based on a protocol resulting from said mode determination.
2. A memory card according to claim 1 , wherein said mode determination for the memory card is performed in response to reception of an initialization command to the memory card.
3. A memory card according to claim 1 , wherein, when said mode determination is performed, said interface unit sets an interface mode to a first operating mode in response to a HIGH level of said select terminal, and sets the interface mode to a second operating mode in response to a LOW level of said select terminal.
4. A memory card according to claim 3 , wherein said memory card is based on a Multimedia Card standard, said first operating mode is an SPI mode, and said second operating mode is an MMC mode.
5. A memory card according to claim 1 , wherein a selection of a low resistance value of the pull-up resistance is performed stepwise and the stepwise selection assumes that a lower resistance value is selected earlier.
6. A memory card according to claim 1 ,
wherein said plurality of external terminals includes a data terminal coupling to a pull-up resistor, and
wherein said interface unit selects a relatively low resistance value for the pull-up resistance of said data terminal during a period after a write command until a start bit of data to be written which is supplied to said data terminal is detected, and selects a relatively high initial resistance value after said detection of the start bit.
7. A memory card comprising:
a plurality of external terminals including a select terminal; and
an internal circuit having erasable and writable nonvolatile storing means,
wherein said internal circuit lowers , in a mode determination period for performing a mode determination in response to an initialization command and based on an input from said select terminal, a value of a pull-up resistance of said select terminal before a determination timing, raises the resistance value of the pull-up resistance to an initial resistance value after said mode determination period, and then starts communicating between an outside device of the memory card based on a protocol resulting from said mode determination made using said lowered resistance value.
8. A memory card comprising:
a plurality of external terminals including a data terminal; and
an internal circuit having erasable and writable nonvolatile storing means,
wherein said internal circuit lowers, during a period after receiving a write command until receiving a start bit of data to be written which is supplied to said data terminal is detected, a value of a pull-up resistance of data select terminal for a mode determination, raises the resistance value of the pull-up resistance to an initial value after said detection of the start bit, and then starts communicating between an outside device of the memory card based on a protocol resulting from said mode determination made using said lowered resistance value.
9. An electronic device comprising:
a plurality of external terminals including a select terminal; and
an internal circuit,
wherein said internal circuit lowers, in a mode determination period for performing a mode determination in response to an initialization command and based on an input from said select terminal, an input impedance of said select terminal before a determination timing, raises the input impedance to an initial value after said mode determination period, and then starts communication between an outside device of the memory card based on a protocol resulting from said mode determination made using said lowered impedance value.
10. An electronic device comprising:
a plurality of external terminals including a data terminal; and
an internal circuit,
wherein said internal circuit lowers, during a period after receiving a write command until receiving a start bit of data to be written which is supplied to said data terminal is detected, an input impedance of select terminal for a mode determination, raises the input impedance to an initial value after said detection of the start bit, and then starts communication between an outside device of the memory card based on a protocol resulting from said mode determination made using said lowered impedance value.