Control system for dot matrix line printer

Abstract

A control system for a dot matrix line printer/plotter apparatus for producing hard copy printout of digitally represented data. The apparatus utilizes one or more hammer banks, each mounted for reciprocal linear movement across a paper web moving therepast. Each hammer bank carries N hammer assemblies, each of which can be selectively actuated to print a dot in any of D columns in any of C characters as the bank sweeps across the paper web. The control system includes an input/output (I/O) microprocessor and a print control microprocessor, each connected so as to have access to a common random access memory (RAM). A portion of the RAM is used as multiple line buffers. Each line buffer is used to store all the character bytes which define a character line to be printed. The I/O processor accepts externally supplied data and loads character bytes for each sequential character line into a different line buffer. During each hammer bank sweep, the print control processor operates with a mapper subsystem to access character bytes in the appropriate sequence from the line buffer storing the character line to be printed. For each of C.times.D dot positions during each sweep, N character bytes are sequentially processed to derive a dot data bit for each such byte. A timing circuit controlled by the print control processor supplies shuttle step and hammer actuate (fire) pulses to a shuttle stepper motor and the hammers, respectively.