A pocket calculator, which is pretty unusual for normal peoples' usage, is the model
"Programmer" from Texas Instruments: This calculator, which appeared on the market in 1977 and
which was produced several years, is only capable of the four standard calculations, but is
also able to calculate in the hexadecimal and octal number system. And with a few hints, you can
also work with binary numbers.
Those calculators were't suitable for normal households, but were mainly used by software
developers and computer programmers, which had to calculate bit by bit because of the power-less
computers with very tiny memories that time.
As interesting as the TI Programmer is by its special calculations, as boring is it in its
technical construction. More about that later.
|case lock in battery compartment|
Case and Keyboard
The plastic case of the TI Programmer consists of two case parts, which are tied together
only by a few stong plastic barbs. No screw, nothing expensive at all. Simple, but efficient.
The upper case half has got a red inlay on its upper third. This inlay is partially tilted and covers
the LED display. Beyond the display, there's the embossed "Texas Instruments" logo. The whole inlay is
surrounded by a silver colored frame.
The rest of the calculator is used from the keyboard and its aluminium cover plate. This brown plate
is printed in white and blue.
The keyboard is simple constructed: There are fourty(!) keys, internally covered by a foam
(which does not last that line), which press on the key plates and give an acustically and
haptically feedback. The keys hardly bounce, but for some reasons, they are pretty slow to use.
|keyboard: contact keys|
This calculator does not have an On/Off switch, but is instead activated and switched
off by two keys. This way, TI could save a real switch, which needed a stronger case and
was prone to misfunctioning.
|keyboard: inner key side|
The inner construction of the calcualtor was quite revolutionary for 1977, but on the same
time very boring, too. Except the keyboard and the mainboard, which only contains one chip and
the LED stick, there are no further parts used. No resistors, no capacitors, no transformers,
no forther ICs.
TI really perfectionized the "Calculator On A Chip".
The very bright LED display with its strong magnifying bubbles was up-to-date that time.
Due to the small size of the light emitting fields (they had to keep the power consumption as
low as possible), the tiny digits had to be enlarged massively by strong bubbles. The
disadvantages of that technics were, that the display seems to lay deep down in the case and
even worse, it is not possible to look at it sideways or at an tilting angle.
The display is driven as usual in a multiplexing way, but here, the multiplexing frequency
seems to be quite suboptimal since the display flickers noticeably.
To save even more power, after 30 seconds without use interaction, the display is switched
off and only a moving dot reminds the user, that the calculator is still powered on. The last
value can be brought back into the display by pressing the "=" key.
|moving dot in powersave mode|
After about five minutes without any entries, the calculator switches off automatically.
|mainboard with CPU and LED display|
The TI-Programmer uses the "Calculator On A Chip" ZA0675NL CPU. In the calculator described
here, this chip was made in week 19, 1979 in Singapore.
The construction of that calculator is identical to the TI-30; they only differ by the used
CPU (which probably only differs by the firmware).
The normal calculating capabilities of the TI Programmer are not very
spectacular: In the normal mode, it can only do the four standard calculations,
up to four brackets and has got a simple memory with a summary function.
In the hexadecimal- and octal more, there are a number of further calculating operations
such as the 1 complement, AND, OR, XOR and bitwise shifting. The hexadecimal mode is
indicated by a double apostrophe; the octal mode by a simple apostrophe.
The calculation range goes up to 99999999, ocal to 37777777 (8388607 decimal = 2^23-1) and
hexadecimal to 7FFFFFFF (134217727 decimal = 2^27-1).
Overflow and division are indicated by a display full of "E"s:
The memory function is realized by three keys; there's no display indicator:
"STO" stores the displayed number, with "RCL", the memory store can be recalled into
display, and with "SUM", the current displayed number is added to the memory
As most calculators of Texas Instruments, the TI-Programmer also contains a so-called
"Batterypack", here of the type BP-8, which consists of two rechargable AA cells, who
generate the neccessiary voltage of 9V DC. The AA cells are recharged by an external
transformer, which delivers 8.5V AC. During the recharge, the calculator can be
used, of course.
Unfortunately, the integrated accus leak after a while, since the calculator uses
a little bit of electricity, even when it is switched off.
Such a leaked AA cell pair can be replaced by an expert.
|inside the batterypack|
Some data regarding the power consumption:
The consumption of the calculators on its 9V connector is 16µA (=0.15mW), when
switched off, is 12mA (=0.1W) when only one zero is shown, is 44mA (=0.4W), when
all digits are on and on the power-saving mode, it still consumes 7.3mA (=0.065W).
The 0.4W were undercutted by calculators with VFD display, and those displays
were also larger and readable from all positions. But the drawback of them were,
that they needed a number of external parts, which were not possible on a
"Calculator On A Chip" design.
The TI-Programmer is a technical rather boring, but due to its unusual
functions rare and interesting pocket calculator. Such a model is an
enrichment of a collection.
|Manufacturer||Texas Instruments (TI)|
|Display||8+1 digit LED|
|Number of keys ||40|
|Functions||+ - * / M HEX OCT AND OR XOR SHIFT 1C ( )|
|Entry logic (classification) ||ALG (BGAA)|
|1 + 0.000 = ||1. |
|0 / 0 = ||Error |
|Power supply ||2xAA (internal)|
|Size||14,7 x 7,7 x 3,4cm|
|Original Price||DM 198,00|