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Part 4: Technical Reference
2. FIRMWARE
2.1 Interface
This printer's interface supports compatible mode, nibble mode, and ECP mode in
compliance with the IEEE 1284 Parallel Interface Standards. The compatible mode is a
uni-directional data transfer protocol similar to the Centronics interface conventional
protocol. The nibble mode and ECP mode are bi-directional data transfer protocols
used to transfer to the host computer the status data, including the device ID, printer
status, etc. The printer uses the compatible mode or the ECP mode (forward transfer)
when transferring print data. It should be noted, however, that the computer must be
set to ECP mode for the printer to operate in ECP mode.
2.1.1 Compatible mode
In compatible mode, data is transferred in 8 bit units. Data gets transferred by the
handshake between the STROBE, BUSY, and ACKNLG signals. When data (Data 1-8)
and the STROBE signal are received from the host computer, the printer controller
controlling the parallel interface outputs BUSY and latches the data on the falling
edge of the STROBE signal. After outputting BUSY, the printer controller transfers
the latched data into the receive buffer inside the DRAM through the DRAM dedicated
bus. When the printer controller is finished writing data into the receive buffer inside
the DRAM, it generates the ACNKLG signal and turns BUSY "Low" to indicate it is
ready for the next data input. This printer has a short default ACKNLG to reduce the
length of BUSY "High," making the printer response time shorter, thus making high
speed printing possible.
0.5 u s 0.5 u s 0.5 u s
Min.
Min. Min.
DATA 1 to 8
STROBE
BUSY
ACKNLG
Figure 4-9 Interfacing Timing (Compatible Mode)
0.9 u s or 4 u s
4-10
BJC-6000
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