CONTROL UNIT FOR CONTROLLING PRINTING HEAD OF A SERIES PRINTER

摘要

1422984 Control of printers SOC LAGOBAX 23 May 1973 [25 May 1972] 24729/73 Heading G4H A print head control unit comprises a buffer 301, means for returning the head to the beginning of a line when the characters in the buffer have been printed, and means for rapidly returning the head to the next printing position along the line when new characters have been stored in the buffer. The addresses in the buffer of the last character to be entered and the next character to be printed are recorded in counters AE, AS which are incremented by 1 at the time of each character input and output respectively on lines 305, 306. A comparator 304 compares the addresses to produce two signals OKS (print next character) or OKE (input new character). The print head position is indicated by the count accumulated in a counter 310 which is incremented as the print head moves from character to character. When AR = AS (i.e. all the characters have been printed) the contents of 310 are transferred to a counter register 312 while the print head is returned to the beginning of the line. New characters are stored in 301, and the print head advanced along the line, decrementing 312 as it does so, until the last printed position is reached; a decoding circuit 313 detects a count of zero in 311, and printing is resumed. Provision is made (314-319) for recognizing and performing functions such as carriage return and tabulation. The printer may receive data from a keyboard 403, Figs. 4, 5 (not shown), and/or from a remote computer connected thereto by modems (404-406).