Appendix B. LFSR Definition
The Plug and Play ISA cards use a linear feedback shift register (LFSR) to generate data patterns needed to provide an initiation key protocol and to provide a checksum verification during serial data read in the isolation protocol.
The LFSR is an 8-bit shift register that resets to the value 0x6A. The feedback taps for this shift register are taken from register bits LFSR[0] and LFSR[1].
Figure B-1. Initiation Key LFSR