Some application programs require a unique configuration. If the printer is notworking properly in the configuration you have selected, contact an IBM servicerepresentative.IEEE 1284 Parallel InterfaceThe IEEE 1284 is a parallel interface with bidirectional capabilities. Features includethe 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 workaround this and send data via other operating modes, such as Nibble Mode whichis discussed later.Less user interaction. The host can ask the printer about printing status andsupported features, such as fonts and internal errors. For example, instead ofhaving to physically check if the printer has run out of paper, you can create aprogram to query this from the host. The printer will respond and a message willdisplay on the host.Operating ModesThe 1284 supports three operating modes, which are determined by negotiationbetween the printer and the host.Compatibility ModeThis mode provides compatibility with a Centronics or PC Parallel interface (seeTable 8). Data is transferred from the host to the printer in 8-bit bytes over the datalines.Compatibility Mode can be combined with Nibble and Byte Modes to providebidirectional communication.Nibble ModeEight bits equals one byte. When a byte of data is sent to the printer, the eight bitsare sent over eight data lines.Some devices cannot send data over their eight data lines. To bypass this, the 1284permits data to be sent as half a byte over four status lines. (Half a byte equals onenibble.) 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, andthe host controls the transmission.214 Infoprint 6500 User’s Manual
