<h1>nandps v2_1</h1><p>This file implements a driver for the NAND flash controller.</p>
<p><b>Driver Initialization</b></p>
<p>The function call <aclass="el"href="xnandps_8c.html#addb9f847fae34f6d137f591375a7c962">XNandPs_CfgInitialize()</a> should be called by the application before any other function in the driver. The initialization function takes device specific data (like device id, instance id, and base address) and initializes the XNandPs instance with the device specific data.</p>
<p><b>Device Geometry</b></p>
<p>NAND flash device is memory device and it is segmented into areas called Logical Unit(s) (LUN) and further in to blocks and pages. A NAND flash device can have multiple LUN. LUN is sequential raw of multiple blocks of the same size. A block is the smallest erasable unit of data within the Flash array of a LUN. The size of each block is based on a power of 2. There is no restriction on the number of blocks within the LUN. A block contains a number of pages. A page is the smallest addressable unit for read and program operations. The arrangement of LUN, blocks, and pages is referred to by this module as the part's geometry.</p>
<p>The cells within the part can be programmed from a logic 1 to a logic 0 and not the other way around. To change a cell back to a logic 1, the entire block containing that cell must be erased. When a block is erased all bytes contain the value 0xFF. The number of times a block can be erased is finite. Eventually the block will wear out and will no longer be capable of erasure. As of this writing, the typical flash block can be erased 100,000 or more times.</p>
<p>The jobs done by this driver typically are:</p>
<ul>
<li>8/16 bit operational mode</li>
<li>Read, Write, and Erase operation</li>
<li>Read, Write cache operation</li>
<li>Read, Write Spare area operation</li>
<li>HW Error Check and Correction (ECC)</li>
</ul>
<p><b>Write Operation</b></p>
<p>The write call can be used to write a minimum of one byte and a maximum entire flash. If the address offset specified to write is out of flash or if the number of bytes specified from the offset exceed flash boundaries an error is reported back to the user. The write is blocking in nature in that the control is returned back to user only after the write operation is completed successfully or an error is reported.</p>
<p><b>Read Operation</b></p>
<p>The read call can be used to read a minimum of one byte and maximum of entire flash. If the address offset specified to read is out of flash or if the number of bytes specified from the offset exceed flash boundaries an error is reported back to the user. The read is blocking in nature in that the control is returned back to user only after the read operation is completed successfully or an error is reported.</p>
<p><b>Erase Operation</b></p>
<p>The erase operations are provided to erase a Block in the Flash memory. The erase call is blocking in nature in that the control is returned back to user only after the erase operation is completed successfully or an error is reported.</p>
<p><b>Page Cache Write Operation</b></p>
<p>The page cache write call is same as write call except that it uses cache commands to write. This enhances the performance. This operation can't be performed on OnDie ECC with internal ECC enabled. There is no way to disable internal ECC for OnDie ECC flash parts in current driver. This operation is tested with Spansion S34ML04G100TFI00 flash. We have to use this operation only on the flash parts which supports program page cache command.</p>
<p><b>Page Cache Read Operation</b></p>
<p>The page cache read call is same as read call except that it uses cache commands to read. This enhances the performance. The read cache random command is used since the HW ECC block doesn't support commands without address for starting ECC. This operation can't be performed on OnDie ECC with internal ECC enabled. There is no way to disable internal ECC for OnDie ECC flash parts in current driver. This operation is tested with Spansion S34ML04G100TFI00 flash. We have to use this operation only on the flash parts which supports read page cache command (random).</p>
<p><b>Write Spare Bytes Operation</b></p>
<p>This call writes to user specified buffer into spare bytes of a page.</p>
<p><b>Read Spare Bytes Operation</b></p>
<p>This call reads spare bytes of a page into user specified buffer.</p>
<p>This driver is intended to be RTOS and processor independent. It works with physical addresses only. Any needs for dynamic memory management, threads, mutual exclusion, virtual memory, cache control, or HW write protection management must be satisfied by the layer above this driver.</p>
