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News Archive - Texas Instruments TMS 1802 Calculator Chip Introduction


Texas Instruments TMS 1802 Calculator Chip Introduction News Article
Computer Magazine, November, 1971

Article announcing Texas Instruments' September, 17, 1971 introduction of its groundbreaking TMS 1802 "calculator on a chip" integrated circuit. Although Mostek had introduced a single-chip calculator IC shortly before to the introduction of the TMS 1802, what made the TMS 1802 unique and especially marketable is that it was essentially a simple reconfigurable general-purpose computer on a chip, including mask-programmed ROM (for program storage), mask-programmed I/O interface (configurable for different display types, e.g., 1 of 10(Nixie), 7-segment, 8-segment, etc.), along with a small amount of RAM (for working register storage and state information) that allowed the same general chip to be configured for different calculator functions by changing a mask used during the construction of the chip. This flexibility allowed different mask versions of the same chip to provide differing calculator functions, while other single-chip implementations were hard-coded for specific calculator functionality and I/O interfacing. While the Busicom 141-PF calculator was the first calculator to use a microprocessor (the Intel 4004) to run the calculator, a number of chips, including separate ROM, RAM, and shift-register I/O interface chips had to be added along with the 4004 microprocessor to provide the full implementation of the calculator. The TMS 1802 chip was the first in what became the TMS 0100-series of calculator on a chip ICs that were the heart of hundreds of different calculators, including some of Texas Instruments' early machines such as the TI-3000.