The parallel interface transfers data in one direction only: from computer to printer. The
data path is 8 bits wide. The printer and the computer synchronize data transfer with the
interface signals, -STROBE, -ACKNLG, and BUSY.
When the computer is ready to send a byte of data to the printer, it puts the byte of data on
the data lines (DATA 1 through DATA 8). Then the computer sends a -STROBE pulse to
the printer. The printer responds with a BUSY signal.
When the printer receives the data, it pulses the -ACKNLG line. This signals the computer
that the printer has read the byte of data into the printer memory If the printer buffer is
not full and it can receive more data, it removes the BUSY signal.
The timing charts that follow illustrate the data and handshake lines during the transfer of
one data byte from the computer. DATA 1 through DATA 8 and the -STROBE line are
driven by the computer; the -ACKNLG line is driven by the printer.
Figure 1-3 Interface Timing
Chapter 1: General Description