Ack Reverse [Output]
This signal remains High when data is sent from the host computer to the printer. It
remains Low in the reverse data transmission phase.
When switching from the forward to reverse data transmission phase, this signal
changes to Low, to indicate that a request to switch modes has been received, in
response to the fall of the Reverse Request (INIT) signal, which is sent by the host
computer to request the switch.
This signal changes to High, to indicate that the request to switch modes has been
received, when the Reverse Request (INIT) signal rises.
Xflag [Output]
This signal is always High in ECP mode.
Host Ack [Input]
When data is sent from the host computer to the printer, this signal indicates
whether the signal information on the data bus is data or command information
(Low: Command information; High: data).
In reverse data transmission, this signal is used for handshaking with the Periph
Clk (ACKNLG) signal.
When the host is ready to receive data from the printer, this signal changes to Low,
then changes to High when the data has been received.
Reverse Req [Input]
This signal changes to Low during the recovery phase (resending data) when data is
sent from the host computer to the printer.
This signal changes to High in response to the lowered Ack Reverse (PE) signal.
This signal changes to Low on transition from the idle state in the forward data
transmission phase to the reverse data transmission phase (when data is sent from
the printer to the host computer).
When Low, this signal indicates reverse data transmission.
The signal changes to High on transition from reverse data transmission to forward
data transmission.
Periph Req [Output]
This signal changes to Low when, during forward data transmission, the printer
requests reverse data transmission.
When the host computer changes from forward data transmission to reverse data
transmission, this signal changes to High at the same time as the Ack Reverse (PE)
signal in response to the fall in the Reverse Request (INIT) signal, which requests the
switch in modes by the host computer.
1284 Active (Input)
This signal goes High at the start of the negotiation phase and remains High in ECP
mode to indicate that the printer is operating in bidirectional mode. It changes to
Low in the termination phase on exiting ECP mode.
2-17
BJC-7100
Part 2: Product Specifications
