GB1457880A - Calculator data storage system - Google Patents

Abstract

1457880 Calculator system TEXAS INSTRUMENTS Inc 14 Dec 1973 [11 June 1973 (3)] 58042/73 Heading G4A A calculator implemented on semi-conductor integrated circuit chips is provided with one or more additional data stores each formed on an integrated circuit chip. The calculator may be as described in UK Specification numbers 1,401,204 and 1,401,265 and the additional data storage chips may be of the kind described in Specification 1,401,203 and U.S. Specification number 3,851,313. Each storage chip may provide ten, sixteen digit registers and has four data input/output leads for receiving address data and for exchanging data with the calculator in the form of BCD digits parallel by bit serial by digit, and control inputs. Accessing an additional data storage chip occupies four instruction cycles. During the first the chip responds to a FLAG control input from the calculator indicating that the data following is address data, any data appearing at the data inputs being otherwise ignored. In the following cycle the first, third, and fourth digits of a sixteen digit word supplied by the calculator designate respectively whether the operation required is input or output (relative to the storage chip) or the clearing of a specified register or registers, the particular register involved, and the particular chip involved, the remaining digits being unused. Each chip has four prewired inputs for comparison with the chip select digit, there being a further input to allow up to 32 chips of additional storage to be addressed. In the third cycle the FLAG control signal is reset and in the fourth sixteen digits of data are transferred between the calculator and the selected register or the selected chip. It is stated that a one digit delay occurs in the calculator and the additional storage chips are arranged to receive data from the calculator and perform a right shift, the last digit being buffered until the right shift has been completed, and to transmit data to the calculator one digit early. Clear operation may involve all registers in all additional storage chips, all registers in a selected chip, or selected registers in a selected chip. Address decoders used to select a register for data output to the calculator are powered only at times within a cycle of the system when they are required in order to reduce the power drain.