
8201, 8202, 8203, 8204 Acceleration Processor Data Sheet, DS-0157-05
Page 31
Exar Confidential
Real time verification may be enabled or disabled via software. If enabled, real time
verification will reduce the performance of small packet (< 2K bytes) LZS and GZIP/Deflate
compression operations. Enabling real time verification will slightly increase the 820x power
consumption (< 0.05W).
2.1.3.1
Compression Engine Real Time Verification
The Compression engine contains one compression core and one decompression core for
LZS and GZIP/Deflate compression operations. Data for compression operations in the
encode direction will be automatically decompressed to verify that the decompressed CRC
matches the original CRC of the raw data. The Compression engine also employs an ECC in
its FIFO.
For compression operations in the encode direction, raw data with an embedded CRC is
compressed by the compression core. The compressed data is then decompressed to verify
that the decompressed CRC matches the original input CRC. If the CRCs do not match, the
Compression engine reports a CRC error to the host. To add further real time verification, a
6-bit ECC is added to the compressed data before it is written to the destination FIFO. This
ECC is verified by the LZS Engine when reading data out from the destination FIFO.
For compression operations in the decode direction, the compressed data with an
embedded CRC is decompressed in the decompression core. The decompressed CRC is
verified by the decompression core, and if an error is detected it will be reported to the
host. If CRC32 is not enabled, this CRC check is also disabled.
Figure 2-2 illustrates LZS real time verification in the Compression engine for encode and
decode operations. In the following figures, a CRC in parenthesis, as in RAW (CRC),
signifies that the CRC is embedded into the data. A CRC that is added to a value, as in RAW
+ CRC, signifies that the CRC is in a header, separate from the data.