Patent GB-1112221-A (GB)
Title: Improvements in data processing systems
Inventor: WALTER GEORGE OSCAR
IPC: G06F3/06
Filed: 1964-08-21
Abstract: 1,112,221. Code converters. A.P.T. ELECTRONIC INDUSTRIES Ltd. 20 Aug., 1965 [21 Aug., 1964], No. 34388/64. Heading G4H. General. Input code combinations are qualified by a decision code, e.g. a case shift code, in a first code convention, and are converted to a code combination, also qualified by a decision code, in a second code convention. In a first embodiment, tape reader 1 provides the input code combinations and associated case code combinations. Code combinations which have the same meaning irrespective of a preceding case code are decoded at 8 to provide a signal on a respective highway 11. Case code combinations are decoded at 7 and set store 15 by way of highways 10. All other code combinations have meanings which are dependent on the last preceding case code and after being decoded at 9 provide a signal which is routed by gates 13, 14 to the appropriate highway 12 in dependence on the last preceding case stored at 15. A signal on any case invariant highway 11 is encoded at 18 and is applied immediately to tape punch 25 via AND gate 23 which is enabled by a signal derived from one of alternative blocks X or Y signifying that the code combination is case invariant. When an input code combination produces a signal on a case dependent highway 12, it has to be decided whether a new case code has to be punched on the output tape before the corresponding code group. OR gate 39 is connected to those highways 12 corresponding to input and output code combinations which have the same meaning when associated with the same case code, and OR gate 40 is connected to those highways 12 corresponding to input and output combinations which have the same meaning when associated with opposite case codes. The last case code recorded on the output tape is stored at 45. Logic circuit 41 compares the effective input and output case codes and, depending on which of OR gates 39, 40 is producing an output, provides an output at A, B or C. If the effective output case code is correct (no case shift is required), output A enables AND gate 67 to produce a punch drive signal through OR gates 36, 32. Each encoder 20 is connected to a pair of highways 12 to produce a code combination which has one of two meanings depending on the effective output case code, and this code combination passes through AND gate 23 to punch 25. If the effective output case code must be changed, an output B or C is produced depending on whether a change from lower to upper case or vice versa is required. The required case is stored at 69 and store 51 is set whereby the required case is transmitted via one of highways 28 to the corresponding encoder 29 and the appropriate case code is applied to punch 25 at the same time as a drive signal from store 51. Store 45 is set to the recently effective output case and circuit 41 then provides an output at A, which, after the store 51 has been reset at the end of the case code punching operation, passes through AND gate 67 to cause punching of the code combination via the appropriate encoder 20 and AND gate 23. Tape reader 1 is then enabled to read the next input code combination. Several such systems may be connected together via highways 10-12 and 28, the logic circuit 41 in each case being designed for the particular two-code conventions involved. The invention is applicable to cases where a decision code occurs simultaneously with each input code combination, e.g. in the form of two ,extra bits, Fig. 4 (not shown).