Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
489
Application DMA Unit—Intel
®
81341 and 81342
5.7
ADMA Operations
The ADMA can be configured on a per descriptor basis through the Descriptor Control
Word (DC) to performs seven distinct operations in addition to a simple data transfer:
1. In an
XOR operation
, the ADMA generates a parity data stream that is comprised
of the XOR of up to 16 distinct data streams in local memory on a per byte basis.
All of the source data streams and the parity data stream can be up to 16 MB long.
2. In an
XOR operation with P+Q RAID6
, the ADMA generates a parity data
stream, P, that is comprised of the XOR of up to 16 distinct data streams in local
memory on a per byte basis. In addition, the ADMA generates a data stream, Q,
whereby the source data streams have each been Galois field multiplied followed by
an XOR of the resultant data streams on a per byte basis. All of the source data
streams, the P data stream, and the Q data stream can be up to 16 MB long.
3. In a
Dual
XOR operation
, the ADMA generates two parity data streams that is
comprised of the XOR of two source data streams, a Horizontal data stream, and a
Diagonal data stream on a per byte basis. All four data streams may be up to
16 MB long.
4. In a
P+Q Update operation
, the ADMA generates updated P and Q check data
streams. The updated P check data stream is comprised of the XOR of two source
data streams and a P check data stream on a per byte basis. The updated Q check
data stream is comprised of the XOR of the same two source data streams that
have been Galois field multiplied, and a Q check data stream on a per byte basis.
All four data streams may be up to 16 MB long.
5. With the
Zero Result Buffer Check Operation
, the ADMA confirms that the XOR
of all the bytes of the parity stripe with their associated bytes in the streams of
source data results in 00H for the entire byte count. All the source data streams
and the parity data stream can be up to 16 MB long. The results of the check are
written back to the Descriptor Control Word in local memory.
6. With the
P+Q Zero Result Buffer Check Operation
, the ADMA confirms that the
XOR of all the bytes of the parity stripe, P, with their associated bytes in the
streams of source data results in 00H for the entire byte count. Also, the ADMA
confirms that the XOR of all the bytes of the Q data stream, with their associated
bytes in the streams of source data after they have been Galois field multiplied
results in 00H for the entire byte count. All of the source data streams, the P data
stream, and the Q data stream can be up to 16 MB long. The results of the check
are written back to the Descriptor Control Word in local memory.
7. Perform a
Memory Block Fil
l of up to 16 MB of local memory with a 32-bit
constant (CRC Address/Data).
8. Perform a
CRC Generation
on up to 16 MB of a data transfer stream using the
value at CRC Address as a seed (CRC Address/Data). Write the result back to CRC
Address. It is optional to write the data transfer stream to the destination address
during this operation.
The following sections describe the seven ADMA operations in detail and support per
ADMA Channel.