Canon Color Bubble Jet BJC-5000 Series, Service Manual

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2. FIRMWARE
2.1 Interface
This printer supports the compatible mode, nibble mode, and ECP mode which are
compliant with the bidirectional Centronics interface standard (IEEE P1284).
The compatible mode is the same as the conventional Centronics interface-compliant
protocol. When the printer operates as a printer, data is transferred in the compatible
mode or ECP mode. The nibble mode is used for transferring status data such as the
device ID and printer status to the host computer during printer operation. To use the
nibble mode or ECP mode, the setting in the host computer must either be the nibble
mode or ECP mode.
2.1.1 Compatible mode
The parallel interface for the compatible mode transfers data in 8-bit blocks. Data is
transferred with the STROBE, BUSY, and ACKNLG handshake signals.
When the printer receives the data (Data 1 to 8) and STROBE signal from the host
computer, the printer controller which is controlling the parallel interface outputs the
BUSY signal and latches the data at the falling edge of the STROBE signal. After the
BUSY signal is output, the printer controller loads the latched data from the DRAM
bus into the receive buffer of the DRAM. After the printer controller finishes writing
data in the receive buffer of the DRAM, it outputs the ACKNLG signal and makes the
BUSY signal LOW. Then, it waits for the next data input from the host computer.
4-7
BJC-5000
Part 4: Technical Reference
Figure 4-7 Interface Timing (Compatible Mode)
300ns
300ns
2.5
µ
s
750ns-500
µ
s
DATA 1 to 8
BUSY
STROBE
ACKNLG