User`s manual

BD2-1220/1221 User’s Manual
13
6. PARALLEL INTERFACE
6.1 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
Other control signals: PE, nFAULT, SELECT
* Bidirectional Parallel Interface (IEEE1284)
The control board supports the bidirectional parallel interface (IEEE-1284).
(1) Compatibility Mode (Host → Printer communication : Centronics compliant)
This control board provides Compatibility Mode, which specifies the Centronics interface
conventionally used for a wide variety of applications.
The control board is placed in this mode by default.
(2) Reverse Mode (Printer → Host communication)
Data transfer from the control board to the host computer is conducted in Nibble or Byte Mode.
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 existing 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.
To make Reverse Mode valid, pins 38 and 39 must be used as well as the parallel interface:
Pin 38: nAutoFD
Pin 39: nSelectIN
The bidirectional communications capability is not available unless these two pins are used. Leave
it at NC if it will not be used.