US 4,400,791 A · Dot matrix printer with compressed character data storage

Abstract

A method and apparatus for performing dot matrix printing in which the storage capacity of a memory used for storing character patterns is significantly reduced and the accompanying decoding process is quite simple. Character patterns to be printed are coded in patterns of normal and half-shifted dots, and data representing both types of dots is stored in a read only memory. Half-shift instructions are stored in the memory to identify which dots are to be printed at half-shifted positions located between adjacent columns in a matrix used as a reference from which the character pattern is encoded. Several half-shift instructions are stored for each row with each instruction corresponding to a plurality of adjacent dot locations in the associated row. In reading out data from the memory, each half-shift instruction is effective until the location of the next half-shift instruction is reached. In a preferred embodiment, the character patterns are encoded so that the memory can be read bi-directionally, printing in two directions.

Claims24

Dependent claims

A printer for printing characters in a matrix pattern of m.times.n dots, comprising:

character data arranged in m rows.times.n columns;
first memory means for storing said character data, said first memory means having at least the same number of addresses as the number n of said columns, each said address including bits corresponding in number to said rows;
u half-shift instructions for shifting selected dots in printed characters, said half-shift instructions being included in designated columns between the columns comprising said character data, said half-shift instructions respectively being stored in a different address immediately preceding the address of columns in said first memory means including data of dots to be shifted, said half-shift instructions including as many bits as said bits in each said data storage address;
means for distinguishing between the state of a first key bit of each address in said first memory means, said first key bit indicating when the data stored in the associated address is said character data or one said half-shift instruction;
reading means for reading out said character data and said half-shift instructions in a first sequence from said addresses of said first memory means, and
printing means for printing said characters in response to data from said means for reading out.

3 more elements

Dependencies are inferred from the claim text.

Dot matrix printer with compressed character data storage

Life of this patent

Dot matrix printer with compressed character data storage

Life of this patent

Abstract

Claims24