Department of Computer Scien

ce and Information Engineering

National Cheng Kung University, TAIWAN

HANEL

OTHER MODES OF THE 8255Printer Signal

‰To understand handshaking with the 8255, we give an overview of printer operation, handshaking signals‰The following enumerates the steps of communicating with a printer

¾1. A byte of data is presented to the data bus of the printer¾2. The printer is informed of the presence of a byte of data to be printed by activating its Strobe input signal¾3. whenever the printer receives the data it informs the sender by activating an output signal called ACK (acknowledge)¾4. signal ACK initiates the process of providing another byte of data to printer

‰Table 15-2 provides a list of signals for Centronics printers