Some application programs require a unique configuration. If the printer is not
working properly in the configuration you have selected, contact an IBM service
representative.
IEEE 1284 Parallel Interface
The IEEE 1284 is a parallel interface with bidirectional capabilities. Features include
the following:
Faster data transmission. Timing of the signals has been reduced.
Bidirectional communication. Both the host and the printer can send data.
Versatility. If a device cannot send data along particular lines, the 1284 can work
around this and 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 1284 supports three operating modes, which are determined by negotiation
between the printer and the host.
Compatibility Mode
This mode provides compatibility with a Centronics or PC Parallel interface (see
Table 8). 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 1284
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.
214 Infoprint 6500 User’s Manual
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