Canon BJC-55 Service Bulletin page 69

Part 2: Product Specifications
BJC-50
ERROR [Output]:
The printer sets the ERROR signal low if the printer detects an error or out-of-paper
condition.
SELECT IN [Input]:
The DC1 and DC3 control codes become valid when this signal is high and invalid at
low. The signal level is detected only when the printer is powered on and when the
INIT signal is initialized.
NIBBLE MODE
STROBE [Input] (Host Clk):
STROBE signal is always high to prevent the printer from reading data.
DATA 1-8 [Input] (Data 1-8):
Not used
INIT [Input] :
Not used
AUTOFEED XT [Input] (Host Busy):
A low signal indicates that data can be received. This signal is high after data is
received.
SELECT IN [Input] (1284 Active):
SELECT IN signal is high at the beginning of negotiation and remains high
throughout the nibble mode. This indicates that the printer is operating under
bidirectional mode. After completing the nibble mode, SELECT IN signal is low.
ACKNLG [Output] (Ptr Clk):
By lowering ACKNLG signal, the printer informs the computer that the data has
been outputted. When the AUTO FEED XT signal from the host computer is raised
to high, ACKNLG signal responds by becoming high.
BUSY [Output] (Ptr Busy):
BUSY signal outputs data to the host computer. The third bit byte data is outputted
first, followed by the seventh data.
P.E. [Output] (AckData Req):
PE signal outputs data to the host computer. The second bit byte data is outputted
first, followed by the sixth data.
SELECT [Output] (X flag):
SELECT signal outputs data to the host computer. The first bit byte data is
outputted first, followed by the fifth data.
ERROR [Output] (Data Avail):
ERROR signal outputs data to the host computer. The 0 bit byte data is outputted
first, followed by the fourth data.
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