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I am working on interfacing a micro-sd card with an 8-bit micro-controller. I do not yet have the hardware so I can not find the solution with an o-scope.

I have been reading the Physical Layer Simplified Specification Version 3.01 and I found this:

As long as the card is busy programming, a continuous stream of busy tokens will be sent to the host (effectively holding the DataOut line low). (p. 117)

This seems to contradict all the examples I have seen, unless there is a logic inversion I am unaware of. In all snippets and discussions I have come across the card is busy while the micro-controller reads 0xFF.

Is there a definitive guide on using the SD card in SPI mode? It seems as though the previously mentioned document could have discussed the SPI voltage levels more clearly. Thank you in advance for your help,

Sam

Jan Hudec
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swinchen
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1 Answers1

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In all snippets and discussions I have come across the card is busy while the micro-controller reads 0xFF.

You are very wrong on this one. The card sends a 0xFF value when it is ready, any other value means it is busy.

Turbo J
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