SD Card OCR "voltage range" meaning ?

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gahelton
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Posted by gahelton: Thu. May 29, 2008 - 04:53 AM
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I have finished the initialization portion of an SD Card interface (SPI Mode) to AVR. When reading the OCR, bit 15 is set indicating a 2.7-2.8 VDD voltage range.

What the heck does that mean ?

All of the information that I've found specifies the operational VDD range from 2.7 - 3.6V. This is considered a "high voltage" range, but seems to be standard at the moment. A "low voltage" range is from 1.6V - 3.6V for SDLV cards.

1. Does the OCR really have any useful meaning ?
2. Should I use CMD8 to query the card for voltage range ?

Thanks

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AVR Microcontrollers, megaAVR and tinyAVR
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embedded-os
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Location: Germany
Posted by embedded-os: Thu. May 29, 2008 - 06:59 PM
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You actual only need the OCR-response if you want to check the SDHC-flag.

    i = MMCWriteCMD_Rx(MMC_READ_OCR, 0, (U08 OS_HUGE *)FFSp_data, 4);
    if(i != FFS_NO_ERR) return(NULL);       // send CMD58 (check R1-part of R3) ..
    FFSp_ver |= (FFSp_data[0] & 0x40) >> 6; // and copy CCS-bit from R3 (SDHC-card)

or see:
http://www.embedded-os.de/index.html?pcfat_port.htm

.

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