Canon BJ-10sx - Manual (Page 105)

DATA
These signals are the 8 bits of parallel data sent from the computer. A
high level indicates a logical 1; a low level indicates a logical 0. The
printer reads the DATA lines when it receives a STROBE pulse.
ACKNLG
The ACKNLG pulse tells the computer that the printer has read the data
from the previous STROBE pulse. An ACKNLG pulse is also generated
when the printer is powered on, or at the completion of the printer
initialization by an INIT signal requested from the computer.
BUSY
When the printer sets BUSY high, it cannot receive data. The BUSY
line goes high in response to a STROBE pulse. This line remains high
until the data is read. BUSY is also high under the following conditions:
z The receive buffer is full of data.
z The printer receives an INIT signal.
z You press the ON LINE button to set the printer off-line.
z A printer error condition, such as out-of-paper, occurs.
PAPER END
The printer sets PAPER END high when it is out of paper or when a
paper jam occurs. PAPER END remains high until you load paper or
clear the jam and press the ON LINE button.
SELECT
When the printer is ready, it sets the SELECT line high. The SELECT
line goes low when:
z You press the ON LINE button to set the printer off-line.
z An error condition, such as out-of-paper, occurs.
z The printer receives the Printer Deselect command. It ignores all
incoming data except DC1, which returns it to a selected state.