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Appendix
IEEE 1284 Parallel Interface
Modes
The IEEE 1284 parallel interface supports the following two modes.
Compatibility Mode
Compatibility mode allows data transmission from host to printer only: Centronics-compatible.
Specification
Reverse Mode
The transfer of status data from the printer to the host proceeds in the nibble or byte mode.
This mode allows data transfer from an asynchronous printer under the control of the host. Data transfers in
the nibble mode are made via the existing control lines in units of four bits (a nibble). In the byte mode, data
transfer proceeds by making the 8-bit data lines bidirectional. Both modes fail to proceed concurrently in the
compatibility mode, thereby causing half-duplex transmission.
Mode
Communication direction
Other information
Compatibility mode
Host
→
Printer communication
Centronics-compliant
Reverse mode
Printer
→
Host communication
Assumes a data transfer from an asynchronous
printer
Data transmission
8-bit parallel
Synchronization
Externally supplied STROBE signals
Handshaking
ACK and BUSY signals
Signal levels
TTL-compatible connector
Connector
ADS-B36BLFDR176 (HONDA) or equivalent product
Reverse communication
Nibble or byte mode
