Printronix P5000LJ Bi-Tronics Parallel Interface, Compatibility Mode, Nibble Mode, Byte Mode

Chapter 15 Bi-Tronics Parallel Interface

Bi-Tronics Parallel Interface

Bi-Tronics is a parallel interface with bidirectional capabilities. Features include the following:

•Timing of the signals has been reduced, thereby speeding data transmission.

•Bidirectional communication. Both the host and the printer can send data.

•Versatility. If a device cannot send data along particular lines, the Bi- Tronics interface can send data via other operating modes, such as Nibble Mode which is discussed later.

•Less user interaction. The host can ask the printer about printing status and supported features, such as fonts and internal errors. For example, instead of having to physically check if the printer has run out of paper, you can create a program to query this from the host. The printer will respond and a message will display on the host.

Operating Modes

The Bi-Tronics interface supports three operating modes, which are determined by negotiation between the printer and the host.

Compatibility Mode

This mode provides compatibility with Centronics-like host I/O. Data is transferred from the host to the printer in 8-bit bytes over the data lines.

Compatibility mode can be combined with nibble and byte modes to provide bidirectional communication.

Nibble Mode

Eight bits equals one byte. When a byte of data is sent to the printer, the eight bits are sent over eight data lines.

Some devices cannot send data over their eight data lines. To bypass this, the Bi-Tronics interface permits data to be sent as half a byte over four status lines. (Half a byte equals one nibble.) Two sequential four-bit nibbles are sent over the lines.

Data is transferred from printer to host in four-bit nibbles over the status lines, and the host controls the transmission.

Byte Mode

The printer and host send data to each other along eight data lines (one bit per line).

If bidirectional communication is supported by the printer and the host, the host will take control of the data transfer.

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