Patent GB-1486571-A (GB)
Title: Data store
IPC: G11C7/00
Filed: 1974-09-30
Abstract: 1486571 Digital stores; selective signalling PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 30 Sept 1974 [3 Oct 1973] 42345/74 Headings G4C and G4H A storage system (Fig. 1) includes a metrix of storage elements Mij, one column Mi1 of which are reserved for flag bits, and a scanner SR which controls read-out of successive rows of the matrix, the scanner being stopped when a "1" flag bit is read into section FL of input/ output register IUR and restarted by an external signal 3. The state of the flag bit may be automatically altered after selection of its associated word if a "1" signal exists on terminal 2. Alternatively its state may be changed by a signal on terminal 4. As described the scanner is stepped on each time a "0" flag bit is read out by the enabling output of OR gate 01 applied to AND gate El, the latter receiving clock pulses C1. To select a particular row i, the clock pulses applied to the gate E1 may be counted in a counter (CT, Fig. 2, not shown), at a count of i a comparator (CP) applying an inhibiting signal to the gate E1. The scanner which may be made on the same semi-conductor body as the matrix may be a bucket-brigade register or a shift register composed of bi-stable elements and shiftable in both directions. The matrix and input/output register may comprise one most per cell but core storage may be used. The matrix may comprise a plurality of sections (M0, Ml, M2, Fig. 6, not shown) two of the sections (M1, M2) having a flag column (k<SP>1</SP>, k<SP>11</SP>), the stopping of the scanner being effected when a flag bit is read out from either column or both. If desired an additional flag column (k<SP>1</SP>1) may be included so that more than one flag bit may be associated with each word. In a further embodiment (Fig. 7) the storage device includes two read-only memories ROM1, ROM2, a read-write memory M3 and a keyboard KB and is used for displaying  on a display DS keyed-in data, the data being converted from binary-coded-decimal form to 7-segment code. The binary-codeddecimal code for digits 0 to 9 is held in rows 0 to 9 of ROM1 and the associated 7- segment code is held in corresponding rows of ROM2. When a first digit is entered, for example the digit 6 by operating key T6 to set the flag bit in column fk, scanner SR is stepped until gate E5 is disabled by the output U1 of register F14 becoming zero (that is when row 6 is read out). The contents of the read-out row of ROM 1 are transferred to register R1 and when a "1" flag bit is read out from column K<SP>11</SP> <SP>1</SP> of read/write memory M3 (initially this will be for row 0) the contents of the register R1 are read in to this row. The flag bit of this row is then reset to 0 and the flag bit of the next row set to 1 so that the next digit is read in to the next row. During read out the contents of the rows of memory M3 are successively fed into register R1 and at each read-out scanner SR is operated, a comparator C at comparison of the contents of register R1 and the data read from the memory ROMI enabling gates EA1- EA7 to read out the associated 7 segment code to the display device DS. In a further embodiment (Fig. 8, not shown) the zero row of memory section My is reserved for a flag indication in binary coded decimal form of the next row of Section My to be accessed. If, for example, row 0 stores 1000 indicating that the next access is to be made to row 8 this information is read into and held in register IURY and compared in comparator Co with information read from read-only memory ROM0 which stores in each of its row the binary coded decimal number associated therewith. At equality the scanner is stopped and the contents of the section My at that row read into register IURy. The scan then continues until row 0 is reached. In a further embodiment (Fig. 9, not shown) each of two banks of memories have an associated scanner.