Compuprint 9058 Programmer Manual - Manual (Page 139)

The Parallel Interface
A78408098-003 C.10
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.