Browse Prior Art Database

Query Printer Status

IP.com Disclosure Number: IPCOM000101559D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Davidson, PS: AUTHOR

Abstract

Disclosed is a method for sending data from a printer to a personal computer using the existing IBM PC Type Parallel interface. The data transfer may be initiated by either the PC or the printer.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 56% of the total text.

Query Printer Status

       Disclosed is a method for sending data from a printer to
a personal computer using the existing IBM PC Type Parallel
interface.  The data transfer may be initiated by either the PC or
the printer.

      Data is transferred from the printer to the PC serially over
the SLCT line, using the BUSY line as a strobe.  Upon receipt of a
null byte from the PC, the printer places one bit of data on the SLCT
line and drops BUSY.  The PC, upon seeing BUSY drop, reads the SLCT
line.  It then sends a null byte to the printer to tell it to send
the next bit.  This automatically raises the BUSY line.  This
procedure is repeated until all data has been transferred.

      There are two ways to enter the data transfer mode. The first
is for the PC to send an escape sequence that requests data.  This
escape sequence contains a 2-byte identifier that selects the
requested data.  On receipt of the escape sequence, the printer will
raise the ERROR line and drop BUSY.  This is to indicate that the
printer is ready to send the data.  Printers without this function
will not raise ERROR when they drop BUSY.  If the printer indicates
it is ready to send data, the PC begins sending null bytes to read
the data.

      The second way to enter data transfer mode is initiated by the
printer.  When the printer wants to send data to the PC it raises the
ERROR line and drops BUSY.  This tells the PC that there is data to
be read.  The PC then begins...