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FatFs R0.10c, released November 9, 2014

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Christopher Williams
2015-01-31 09:29:37 -07:00
parent 762b341574
commit 0e89a5798f
79 changed files with 1601 additions and 1367 deletions
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doc/en/dread.html
+5 -4
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@@ -32,9 +32,9 @@ DRESULT disk_read (
<dt>buff</dt>
<dd>Pointer to the <em>byte array</em> to store the read data.</dd>
<dt>sector</dt>
<dd>Start sector number in logical block address (LBA).</dd>
<dd>Start sector number in 32-bit LBA.</dd>
<dt>count</dt>
<dd>Number of sectors to read. FatFs specifis it in range of from 1 to 128.</dd>
<dd>Number of sectors to read in range of from 1 to 128..</dd>
</dl>
</div>
@@ -56,9 +56,10 @@ DRESULT disk_read (
<div class="para desc">
<h4>Description</h4>
<p>The memory address specified by <tt class="arg">buff</tt> is not that always aligned to word boundary because the type of argument is defined as <tt>BYTE*</tt>. The misaligned read/write request can occure at <a href="appnote.html#fs1">direct transfer</a>. If the bus architecture, especially DMA controller, does not allow misaligned memory access, it should be solved in this function. There are some workarounds described below to avoid this issue.</p>
<p>The data read/write operation to the storage devices is done in unit of <em>sector</em>. FatFs supports the sector size in range of from 512 to 4096 bytes. When FatFs is configured to fixed sector size (<tt>_MIN_SS == MAX_SS</tt>, this will be the most case), the read/write function must work at that sector size. If variable sector size is selected (<tt>_MIN_SS &lt; MAX_SS</tt>), FatFs inquires the sector size with <tt>disk_ioctl()</tt> after initialization</tt>.
<p>The memory address specified by <tt class="arg">buff</tt> is not that always aligned to word boundary because the argument is defined as <tt>BYTE*</tt>. The misaligned read/write request can occure at <a href="appnote.html#fs1">direct transfer</a>. If the bus architecture, especially DMA controller, does not allow misaligned memory access, it should be solved in this function. There are some workarounds described below to avoid this issue.</p>
<ul>
<li>Convert word transfer to byte transfer in this function. - Recommended.</li>
<li>Convert word transfer to byte transfer in this function if needed. - Recommended.</li>
<li>For <tt>f_read()</tt>, avoid long read request that includes a whole of sector. - Direct transfer will never occure.</li>
<li>For <tt>f_read(fp, buff, btr, &amp;br)</tt>, make sure that <tt>(((UINT)buff &amp; 3) == (f_tell(fp) &amp; 3))</tt> is true. - Word aligned direct transfer is guaranteed.</li>
</ul>