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- # Accessing SD cards
-
- SD cards support the SPI protocol. If you have a SPI relay
- (doc/hw/spi.txt) and a driver for it that implement the SPI
- protocol (doc/protocol.txt), you're a few steps away from
- accessing SD cards!
-
- What you need to do is to add the SDC subsystem to your Collapse
- OS binary. First, define SDC_DEVID to a mask selecting the
- proper device on your SPI relay (this is what is sent to
- "(spie)"). For example, a SDC_DEVID or 1, 2, 4, or 8 would
- select SPI device 1, 2, 3 or 4.
-
- The subsystem is loaded with "423 436 LOADR".
-
- Initialization of the SDC system is done in multiple steps.
- First, the BLK system needs to be initialized with "BLK$". Then
- you can plug SDC@ and SDC! into BLK with "' SDC@ ' BLK@* **!"
- and "' SDC! ' BLK! **!". That only needs to be done once per
- boot.
-
- Then, the SD card that was inserted needs to be initialized. You
- can do it with "SDC$". If you have no error, it means that the
- system can spek to your card, that sync is fine, etc. You can
- read/write right now. SDC$ needs to run every time a new card
- is inserted.
-
- Collapse OS' SDC drivers are designed to read from the very
- first 512 sector of the card, mapping them to blocks
- sequentially, 2 sectors per block.
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