Abstract: A system and method for allowing uni-directional data to be read in the reverse direction as well as the forward direction uses a data buffer to reverse the order of data read from storage media. Data are read from the storage media in the reverse direction and stored in a data buffer. Pointers are set up to track record boundaries of the data storedin the data buffer. The data are read from the data buffer in the opposite direction from which they are stored and sent to a host in the forward direction. Cyclic redundancy checks can be performed as data are read from the storage media in the reverse direction and read from the data buffer in the forward direction.

Abstract: The present invention discloses a method and apparatus for computing CRC codes for fixed length page buffers of user data where the user data arrives from a transmission device in variable length packets with the packet contents being out of sequential order. The received data is written to a storage device after being restored to the correct sequential order. The data packets are comprised of a header portion and a data portion. The transmission and compression methods commonly employed by the transmission device dictates that the header portion of each packet follows the data portion. The present invention computes a complete CRC code for the data stored in a page buffer in real time as the packets are received by using several registers for saving intermediate CRC codes and circuitry to combine partial CRC codes for those packet portions received out of order.