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TMS1000: the first commercially available microcontroller



We use microcontrollers without even thinking about it, in such projects in which once we would have to work with a bunch of logic chips of the 74th series. But which of us has ever thought about the evolution of microcontrollers? It's time to go back a few decades and look at the first commercially available microcontroller, Texas Instruments TMS1000.

Imagine a world without microcontrollers



The Texas Instruments 1978 Speak & Spell toy was a typical example of using the TMS1000.

It would not be an exaggeration to say that without microcontrollers, many of the home-made projects displayed on sites like Hackaday would not have been done. Those of us who remember the time before microcontrollers accessible to the public and easy to program will be able to confirm that computer control in the project of creating a small device, although it was possible in principle, but instead of using a single chip, you would have to make an entire computer system. I remember the systems assembled on Veroboard prototyping boards (from Vero Precision Engineering Ltd) based on Z80 processors, and besides the Z80, there were EPROM, RAM chips, 7400 series chips on the board, and peripheral chips like 6402 UART or port 8255 I / O. To blink an LED or to follow microswitches - such tasks required serious expenses, both in terms of labor and cost, therefore we decided on this only when they were necessary for the project. For me, everything changed in the early 1990s, when the first available microcontrollers with EEPROM on board entered the market, but by that time the chips themselves had already existed for a couple of decades.

This may seem strange today, but for an engineer from the 1970s, a desktop calculator was more interesting than a desktop computer. Nevertheless, many of the first microcomputers were designed with an eye on calculators, such as Intel 4004. Calculator manufacturers contributed to the development of silicon chips, and in Texas Instruments this led to the creation of the first all-on-one microcontrollers that were developed in 1971 as pre-programmed CPUs, on the basis of which it would be possible to make calculators on one chip. Only a few years later, in 1974, the company will release the TMS1000, a microcontroller on a single chip for a wide range of tasks, and this will be the first such chip to go on sale.

It is worthwhile to dwell in more detail on the terminology used, since in 1974 not all modern words were used everywhere. TI touted the TMS1000 as a microcomputer, because it seemed to them an all-in-one computer that did not require external peripherals. Today we would call the microcomputer the device on which you are probably reading this article, descending from the distant ancestor of the Altair 8800 that appeared in the same year, but then the terminology, like technology, was in its infancy. The word "microcontroller" was then used to refer to a computer with built-in I / O - the citation from the 1971 IBM technical bulletin is provided in the Oxford English Dictionary - but, apparently, this definition has not gained universality. Compare with the more modern definition of “system on a chip,” SoC,which means a full-fledged general-purpose computer that gives access to its bus, and not just a set of I / O lines or peripherals, like a microcontroller.

How simple should the microcontroller be?



Internal architecture of the TMS1000 The

TMS1000 was then the first commercially available microcontroller. But what was that chip? In the original line, he had four options, all with the same 4-bit processor of the Harvard architecture , but with a different number of I / O lines and ROM and RAM sizes. The TMS1000 and TMS1200 families had 8192 program bits in RM and 256 bits of RAM, while the TMS1100 and 1300 had twice as much. There were versions with support for high output voltages for controlling vacuum fluorescent indicators, in housings with 28 and 40 contacts. Their internal architecture by today's standards was extremely simple - no register banks or pipelining that could be expected from modern schemes. He did not have such a large assortment of peripherals available for modern microcontrollers, and the I / O relay elements were supplemented by a simple programmable logic matrix. It could be used as an encoder or decoder, for example, in this specification it is used as a decoder for a 7-segment display. Sophisticated software development process for TMS1000




But experimenters could not buy such a chip individually, since its ROM mask could only be programmed at the time of production. All programming went on the mainframe simulator with access sharing supported by TI. As a result of the simulation, the computer produced a stack of punch cards, which, after very complex debugging and testing processes, could be used to create masks for encoding ROM. On request, even the microcode could be changed, having received an extension of capabilities for 43 device instructions. Mask programming also meant that all of the TMS1000s you can find today still contain the programs you made them with; and without context, in the form of the original iron, they will be useless, except in the form of a historical curiosity. However, this does not stop some sellers fromto put heartbreaking price tags on them, but still, if you really need the TMS1000 for the collection, you can buy it at a not very high price.

1970- , ?



CMOS TMS1000

By the 1980s, the world was captured by microprocessors and microcontrollers of 8 and 16 bits, therefore, apart from invisible work in the bowels of TI calculators, the TMS1000 line eventually retired and quietly sailed into the history of electronics. It is interesting to note that some of her contemporaries still work today - you can still buy derivatives of PIC, 8051, Z80 and even 6502, despite the fact that there are no more direct descendants of 4-bit TI processors. One of the reasons for this was the rapid development of technologies, but the difficulty in developing software for them also played a role. The listed 8-bit CPUs are still popular because everyone can take a prototyping board, an EPROM programmer and start writing a program, which is why they spawned the backbone of developers who are well versed in their architecture.Developers for the TMS1000 have to look in the afternoon with fire, and they are clearly not enough to require the development of descendants of 4-bit chips. At one time, several versions of processors with support for an external ROM were developed, but since then the progress has gone forward and has grown by 4 bits.

Today, you may run into the TMS1000 mainly because of an electronic toy from the 70s, such as Speak & Spell from TI itself, or Simon from Milton Bradley. Even these games survived their own processor; today you can buy a modern version of the Simon game from Mattel, and the TI line of educational speech toys from TI continued until the 1990s. However, this processor has left an incredible legacy, and it can still be found today in an electronic device with a microcontroller. If you have such a device, know - you have a small piece of history!

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