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6. PARALLEL INTERFACE
6.1 Bidirectional Parallel Interface (IEEE1284)
6.1.1 Compatibility Mode (Host → Printer communication :
Centronics compliant)
• General description
This printer provides Compatibility Mode, which specifies the Centronics
interface conventionally used for a wide variety of applications.
• Specifications
Data transfer method: 8-bit parallel
Synchronizing method: Controlled by nStrobe signal externally supplied
Handshaking: Handled by nAck and Busy signals
Signal level: All signals are TTL compatible
6.1.2 Reverse Mode (Printer → Host communication)
Data transfer from the printer to the host computer is conducted in Nibble or Byte
Mode. (For details, See “APPENDIX 2. BIDIRECTIONAL PARALLEL INTERFACE”.)
Outline
The reverse mode has been devised to handle data transfer from an
asynchronous printer controlled by a host computer.
In Nibble Mode, data is transferred, 4-bits (A nibble) at a time, using traditional
control lines. In Byte Mode, data is transferred by making 8-bit data lines bi-
directional. Note that either mode cannot work simultaneously with Compatibility
Mode, thus resulting in half-duplex transmission. (For details, See “APPENDIX 2.
BIDIRECTIONAL PARALLEL INTERFACE”.)