GB1380599A - Tabulation control systems for printing apparatus - Google Patents

Abstract

1380599 Printers CASIO COMPUTER CO Ltd 12 Sept 1972 [14 Sept 1971] 42267/72 Heading G4H A tabulation control system for a printer comprises a tab position register 11 for storing a plurality of tab-set positions as decimal values, pulse-driven printing head feed means 19, a printing head position counter 16 for counting the pulses, means for shifting register 11 to produce the next tab position value each time a tabset operation is required, and a coincidence detector 15 responsive to said next tab position value and the output of the printing head position counter 16 for controlling the operation of the printing head feed means 19. Shift register 11 is loaded with a sequence of decimal values representing tab-set positions, each followed by a code T, and the sequence starting with a code S. One or more of the codes T may be followed by a mode-change code C. When a tab key 31 is pressed, a flip-flop 29 is set, causing shift register 11 to begin to circulate. The S code resets a mode order counter 22. The first tab-set decimal value is placed in a buffer register 14, the following T code setting a flip-flop 30 which disables shifting of register 11 and passes pulses from a generator 17 to the printing head feed means 19 (to step the printing head along the line) and to the printing head position counter 16. On equality between counter 16 and buffer register 14, coincidence detector 15 resets flipflops 29, 30. When tab key 14 is pressed again, the second tab-set decimal value is used similarly to step the printing head to the second tab position, and so on. If a mode-change code C is encountered, the mode order counter 22 is incremented by one, as a result of which a coincidence detector 23 detects inequality between this counter and a mode designation counter 24 (initially cleared) to disable setting of flip-flop 30 and resetting of flip-flop 29 so that subsequent tab-set decimal values are ignored until, on the next circulation of register 11, the start code S resets the mode order counter 22. A carriage return key 20 resets the printing head position counter 16 so that the next line can have tab operations performed according to the same pattern. If a mode switching key 25 is pressed, the mode designation counter 24 is incremented by one so that the system will ignore tab-set decimal values prior to the first mode-change code C, and similarly further actuations of this key select successive groups of tab-set decimal values.