US 4,394,685 A · Interface for operating a dot matrix printer for printing a video image

Abstract

An electronic interface for operating a dot matrix printer to print a pattern appearing on a television screen employs video-type signals incorporating field and line sync signals, digitized image signals representative of dots of information along each raster line and dot pulses for synchronizing the digitized image signals. Upon receipt of a print request, a line address counter is incremented by each line sync pulse. A second counter, which is incremented each time the line address counter reaches a maximum count, has its count set into a horizontal position counter at the beginning of each line scan and is decremented synchronously with the dot pulses. The sequentially received dot information is loaded serially into a shift register and is transferred byte-wise in parallel into a location in a random access memory identified by the count in the line address counter when the horizontal position counter reaches a zero count. When the line address counter reaches its maximum count, the interface circuitry prints the stored bytes, representing a "slice" of the raster image in an orientation transverse to the direction of the lines comprising the raster image. Successive "slices" are acquired and printed in a similar fashion to collectively create a completed image.

Claims23

Dependent claims

A method for storing data for use in operating a printer of the dot matrix type from digitized video data comprising a composite sync signal incorporating field and line sync signals, a data signal incorporating digitized image data, and a clock signal incorporating regularly occurring time pulses for use in synchronizing the digitized data signals, said method comprising the steps of:

initiating an acquired data cycle upon detection of a next field signal when the printer is ready to print;
counting line sync signals occurring after the detection of the last-mentioned field sync signal;
counting timing pulses occurring after detection of each line sync signal;
and
selecting a predetermined portion, less than the whole of the image data of each line, in accordance with the timing pulse count, for storage in a random access memory at locations in the memory determined in accordance with the line count associated with the portion of image data being stored.

2 more elements

Apparatus for operating a dot matrix printer from a composite video-type signal comprising signals representing image information for each line of a raster image and field and line sync signals, said apparatus comprising:

means for detecting said field sync signals;
first digital counter means for counting line sync signals after the occurrence of a said field sync signal;
memory means having address inputs cooled to said first counter means for selecting a memory location in accordance with the count in said first counter means;
conversion means for converting said image information signals into sequential digital signals;
said memory means including data inputs coupled to the outputs of said conversion means for writing digital signals from said conversion means into a memory location selected in accordance with said first counting means;
and
second counting and control means for selecting a portion, less than a whole line, of the information of each line of the raster image to transfer into the memory means from said conversion means.

4 more elements

Dependencies are inferred from the claim text.

Interface for operating a dot matrix printer for printing a video image

Life of this patent

Interface for operating a dot matrix printer for printing a video image

Life of this patent

Abstract

Claims23