1. Field of the Invention
The present invention relates to a printer control apparatus.
2. Related Background Art
A so-called serial type recording apparatus (to be referred to as a serial printer hereinafter) having a movable part (to be referred to as a carriage hereinafter) with a recording head reciprocative in a direction perpendicular to a feed direction of a recording medium (to be referred to as a recording sheet or a sheet hereinafter) such as a sheet of paper or an OHP sheet is proposed in various forms of recording heads according to various recording schemes. Recording heads used in serial printers and, particularly, a printer for forming character, graphic, and other images by a dot matrix are classified into a wire dot recording head, a heat-sensitive recording head, a thermal transfer recording head, and an ink-jet recording head.
In a conventional printer of this type, processing for developing recording character codes or the like into dot data and transferring the dot data to a recording head is performed by a central processing unit (CPU).
When a recording speed is increased, carriage control, print data conversion, and its transfer cannot cope with the recording speed by processing of the CPU itself. In order to solve this problem, a line buffer for storing a one-scanning component (i.e., one-line data) of the recording data (print data) for the recording head is arranged, the print data is converted in advance, and the converted data is transferred. However, in so-called bidirectional printing for recording data during reciprocal movement of the carriage, the carriage is completely stopped during development of the next data upon completion of one-line printing, resulting in inconvenience.
When print data transfer is performed by only hardware, the CPU is overloaded to align the currently transferred data with the carriage position although the CPU is free from transfer of data which is being currently printed, and the problem posed by high-speed printing cannot yet be solved.
In an arrangement for recording data while the data is being exchanged with a host device, data exchange must be performed even during printing. When high-speed printing is to be performed, contention occurs between an interruption of an interface arranged to exchange the data and the printing operation, thus posing another problem.