1.At power up this line(DAT3) has a 50KOhm pull up enabled in the card. This resistor serves two functions Card detection andMode Selection. For Mode Selection, the host can drive the line high or let it be pulled high to select SD mode. If the host wants to select SPI mode it should drive the line low. For Card detection, the host detects that the line is pulled high. above is from SD Version 2.00 spec 2.When DAT3 is used for card detection, pulled-up resistor for DAT3 should be unconnected,another pulled-down resistor 3. 4.there is three ways for detect, wwwbbb Post at 2009-4-4 9:56:50 谢谢,学习到东西了 |
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