History and Curiosity

Texas Instruments appears to have been caught out by the arrival of the calculator-on-a-chip from its rival Mostek.  A few months before the announcement of the Mostek MK6010 the journal "Electronics" had reported:
"Like many MOS circuit makers, the Dallas company [Texas Instruments] is working to reduce the number of chips for a calculator set.  Roop [TI's MOS marketing manager] says that designing and building a one or two chip calculator next year 'will be a snap'.
This would make possible a calculator selling at $200 retail.  Even more dramatic, TI is designing an MOS chip which would contain all the electronics for a calculator that would sell for $99—truly a potential high volume consumer product.  And TI is thinking 'very strongly' of selling this bigger custom chip in 1971, he notes.  If TI can get the price of this one chip down to between $15 and $25, then a $99 electronic calculator will be possible, Roop says."

TI responded quickly after the announcement of the Busicom calculator with the Mostek chip, since also in February 1971 'Electronics Design' reported "Two days after Mostek announced its development of a calculator on a chip, another Dallas-based company Texas Instruments said that it, too, was completing development of a one-chip calculator that would be available "off-the-shelf" by June."

The TMS1802 was actually announced in September 1971 and is a very sophisticated device, being in reality a single-chip-microcontroller optimised for use in a calculator.  The journal 'Wireless World' reported "The i.c. contains an eight-digit b.c.d. arithmetic logic unit; a three-register 182-bit random access store; a 3520-bit read-only memory for holding the programme; and timing, output, and control decoders. Floating-point or fixed-point operation calculations can be performed and there is automatic round-off of numbers and leading zero suppression.  Arithmetic and control operations are based on a 4μs single-phase clock system."  Thus the chip has an internal structure based on a processing unit linked to integral RAM and ROM.  By employing different masks for the ROM during manufacture the functionality of the calculator could be adjusted.  Texas Instruments later renamed this integrated circuit the TMS0102 and it was the start of a family of TMS01xx microcontroller chips that could be manufactured to be calculators or dedicated controllers.

The TMS1802 was initially sold on the general market to calculator manufacturers, with Texas Instruments delaying the manufacture and marketing its first calculator, the TI-2500 "Datamath", until July 1972.  Several models of calculator used the TMS1802 including the Sinclair Executive hand-held calculator, the Texet 1 hand-held calculator, and the Advance Wireless World desktop calculator

Early Sinclair Executive calculators used the TMS1802NC "calculator-on-a-chip", here date-coded to 1971, week 37. The two smaller integrated circuits are LED drivers.

At first the Sinclair Executive used the TMS1802NC in a novel way where the power to the chip was pulsed to reduce the power consumption in order to give long life from the button cells used.

In November 1972 the journal IEEE Spectrum reported:
"MOS/LSI family expanded to nine standard 'calculator on a chip' circuits

    The TMS0100 family of calculator-on-a-chip MOS/LSI integrated circuits, introduced by Texas Instruments last year as the TMS1802, has been expanded to nine off-the-shelf circuits.  The TMS1802 is a specific implementation of a basic or host calculator chip.  Any number of operational characteristics can be implemented by the manufacturer using single-level mask programming techniques of the same basic or host design. The only limitations are the size of the program ROM, the RAM storage, and the control, timing, and output decoders.
    Four of the nine calculator circuits are considered preferred types.  The TMS0101 and TMS0103 are the preferred eight-digit circuits.  The preferred ten-digit circuits are the TMS0106 and the TMS0118.
    The TMS0101 has the following features of the one-chip family: floating- or fixed-point result, chain operation, constant operation, protection of result in overflow, underflow in fixed-point mode, leading zero suppression, automatic power-on clear, and automatic sequence and powers.  This eight-digit version uses algebraic keyboard entry—the user presses the keys exactly as he would describe the problem.
    The TMS0103 provides eight digits, four operations, floating or fixed decimal point, constant or chain operation, automatic roundoff, overflow and underflow, leading zero suppression, and automatic power-up clear.  This variation uses the arithmetic keyboard entry system—the same as standard business machines—and is ideally suited for most desktop machines.
    The TMS0106 and TMS0118 are both ten-digit versions.  Both feature a three-position  selectable roundoff that uses a switch to determine how a number will be rounded—up, down, or off—when in fixed-point operation.  The TMS0106 uses arithmetic entry; the TMS0118 uses formula entry.
    All nine of these units are available immediately from stock.  Price in 100-piece quantities for the elght-digit chips is $38.15, and $41.97 for the ten-digit ones."

The TMS0100 series proved to be a very popular family of chips for use in calculators during the 1970s.

By developing the TMS01xx system further TI went on to produce the very successful general-purpose TMS1000 micro-controller series, examples of which were also used in high-specification calculators later in the 1970s

 

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