diff options
Diffstat (limited to 'fatfs/doc/en/dread.html')
| -rw-r--r-- | fatfs/doc/en/dread.html | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/fatfs/doc/en/dread.html b/fatfs/doc/en/dread.html index 2e7c279..e7c2d7d 100644 --- a/fatfs/doc/en/dread.html +++ b/fatfs/doc/en/dread.html @@ -30,11 +30,11 @@ DRESULT disk_read ( <dt>pdrv</dt>
<dd>Physical drive number to identify the target device.</dd>
<dt>buff</dt>
-<dd>Pointer to the <em>byte array</em> to store the read data.</dd>
+<dd>Pointer to the first item of the <em>byte array</em> to store read data.</dd>
<dt>sector</dt>
<dd>Start sector number in 32-bit LBA.</dd>
<dt>count</dt>
-<dd>Number of sectors to read in range of from 1 to 128..</dd>
+<dd>Number of sectors to read.</dd>
</dl>
</div>
@@ -56,12 +56,12 @@ DRESULT disk_read ( <div class="para desc">
<h4>Description</h4>
-<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 < 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>
+<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. When FatFs is configured to variable sector size (<tt>_MIN_SS != MAX_SS</tt>), sector size is inquired with <tt>disk_ioctl</tt> function following <tt>disk_initialize</tt> function.</p>
+<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 unaligned read/write request can occure at <a href="appnote.html#fs1">direct transfer</a>. If the bus architecture, especially DMA controller, does not allow unaligned 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 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, &br)</tt>, make sure that <tt>(((UINT)buff & 3) == (f_tell(fp) & 3))</tt> is true. - Word aligned direct transfer is guaranteed.</li>
+<li>On the <tt>f_read</tt> calls, avoid long read request that includes a whole of sector. - Any direct transfer never occures.</li>
+<li>On the <tt>f_read</tt> calls, make sure that <tt>(((UINT)data & 3) == (f_tell(fp) & 3))</tt> is true. - Word alignment of <tt>buff</tt> is guaranteed.</li>
</ul>
<p>Generally, a multiple sector transfer request must not be split into single sector transactions to the storage device, or you will not get good read throughput.</p>
</div>
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