Compuprint 10200 Programmer Manual - Manual (Page 222)

Interfaces
218
1284 Active (NSelectIn)
Compatibility Mode: Set low by host to select printer.
Negotiation Phase: Set high in conjunction with Host Busy being set low to request a 1284
mode.
Reverse Data Transfer
Phase: Set high to indicate that bus direction is printer to host. Set low to
terminate 1284 mode and set bus direction host to printer.
Reverse Idle Phase: Same as Reverse Data Transfer phase.