Epson 8900 Series - Manual (Page 200)

Communication Interfaces 10-9
Busy Signal
This active-high signal from the printer indicates that the printer is
busy and cannot accept additional data. During data-transfer
operations, the leading edge of the host-generated strobe signal
activates BUSY for each character-transfer cycle. The printer sends an
acknowledge pulse and deactivates BUSY at the completion of each
character-transfer operation (unless the printer is otherwise busy).
BUSY is active (high) under any of the following conditions.
q The host has clocked a character into the receive buffer, but the
printer has not yet acknowledged it.
q The receive buffer is filled to capacity.
q The printer is in its offline state.
q The printer is out of paper or a printer error condition exists.
q One of the control panel menus has been invoked and the printer
has not been returned to its online state.
Fault Signal
The fault (FAULT-) signal from the printer indicates to the host that
an error condition (such as a mechanical failure or a receive buffer
overflow) exists in the printer. A paper-out condition activates both
FAULT- and PE to indicate the condition to the host
Initialize Signal
The initialize (INIT-) signal from the host causes the printer to
execute a power-up reset sequence. During this sequence, the printer
performs its normal self-tests and then assumes its online condition.
Since INIT- is a host-generated signal, the conditions under which it
is generated depend on the type of computer serving as host.