Tychon Incorporated the New Microprocessors And

THE IMPACT OF MICROCOMPUTERS ON AUTOMATED INSTRUMENTATION IN MEDICINE. ADVANCES IN HARDWARE AND INTEGRATED CIRCUITS Jonathan A. Titus Tychon Incorporated P. 0. Box 242 Blacksburg, VA 24060 Introduction The new microprocessors and microcomputers have allowed a wide range of instruments to be automated and they Recent advances in the areas of linear and digital have spawned new instruments which could not be eco- electronics have provided functional building nomically produced in the past. There are some factors blocks which were unavailable, if not unheard of a which must be considered when thinking about micro- few years ago. The revolution in microcomputers is computer applications: a good example. During the 1960's manufacturers were building electronic calculators using hundreds Simplicity When using microcomputers in instruments, of integrated-circuits which represented discreet not only is the circuitry simplified, but so are the gates, flip-flops and registers. In 1970 Texas actions required by the user. Many of the new micro- Instruments announced its integrated-circuit "chip" computer-based instruments are self-calibrating and calculator device and shortly thereafter Intel self-testing and they can perform complex mathematical Corporation announced the first microprocessor chips operations upon the raw data obtained. Evaluation of in the 4004, four-bit family of devices. test results based upon the computer's "past experience" is also possible. These developments were quickly followed by eight, twelve and sixteen-bit microprocessor chips and it Even though computers may be present in instruments, we is now possible to purchase a complete microcomputer do not have to be computer experts to use them. If we for under $1000. had to be electrical engineers or programmers to use microcomputer-based devices, few of us would bother using them. Electronics and Instrumentation Flexibility Microcomputers are flexible devices. What has this revolution in electronics done for They were built to look like small computers so that medical instrumentation and patient care? There are they would be able to tackle a variety of jobs. a number of effects: A single microprocessor chip may find use in thousands of different applications, from medical instruments to Simplicity The first and most obvious effect is one microwave ovens. This flexibility requires that engi- of simplification of the electronic hardware necessary neers and scientists carefully define the problem to be to perform a given task. With the electronics being solved before a solution is attempted. We find, how- integrated into small, integrated-circuit packages or ever, that the flexibility of the microcomputers is "chips" the overall circuitry becomes less complex. expensive and that it is often over-sold. This is important since it improves reliability and allows for easy repair and assembly. Cost Today, microprocessor chips are inexpensive, but this does not necessarily mean that the microcomputer in Cost With the size of the circuitry "shrinking," which they are incorporated will be inexpensive, too. the overall cost of the electronics is less than it The Intel 8080 microprocessor chip has had its price would be if discreet electronic components such as drop from $360 each to just under $20 each, but the transistors and diodes are used. Fewer parts are cost of an 8080-based microcomputer may still be needed, so the cost of assembly, production and expensive. field service are lowered. There are cases where a manufacturer has kept the selling price of an instru- All computers still require power supplies, memory and ment the same as it was before incorporating the input/output (I/O) devices such as teletypewriters and new circuit technology, but he has increased the display devices. While microcomputers are becoming instrument's capabilities by using integrated-circuits lower in cost and while they allow us to do things and the newer, modular electronic packages now avail- unheard of a few years ago, the cost may still be high. able. For example, a simple shift register circuit One of the hidden costs in all compute-based devices cost $50 per bit in the late 1950's, but one can now is the cost of the software or the programs necessary be purchased as an integrated-circuit for about 25¢ to make the computer perform its tasks. Computer per bit. hardware may be coming down in cost, but computer software is still expensive. The more complex the task, and thus the software, the more expensive the software Microprocessors and Microcomputers package will be. Software is generally considered to be a one-time cost since the programs do not have to be When microprocessors and microcomputers became avail- rewritten each time one of the same type of instrument able they were quickly used by instrument manufacturers leaves the factory. to further simplify medical instruments and to reduce their costs. Now, a complete computer could be It is a fact of life that all software contains "bugs." added to an instrument for under $1000. This allowed These program errors may be detected and corrected instrument designers to use computers in applications before a product is sold, but large computer systems where they had been previously too expensive, too may require some time in actual use under varied complex for the job at hand or possibly too big for conditions before all the bugs are detected and portable instruments. corrected. 99 M_Lcocomputer Hardware within the memory device is lost. This is often called volatile memory since data will "evaporate" without the The microDrocessor chips have become more and more constant application of power. This limitation may sophisticated as their prices continue to fall. be easily overcome with an uninterruptable power soujrce The newer mic-oprocessor chips are also easier to use such as a battery pack. than some of the early ones and the newer devices also have miany niew in.structions which make them power- The ROM devices are available in a variety of sizes and ful -oar processing data and making decisions. types, generally selected based upon the type of computer they will be used with and the intended appli- Here are some examples: cation. The ROM devices will maintain the data stored in them indefinitely, independent of power. In this The InteD1 C8( is ani eight-bit microprocessor which way they are particularly useful for storage of program started at a price of $120 each. They are now avail- steps, calibration routines, self-test sequences and able for under $10. This device requires at least constants which will be used again and again. This data 50 to 60 additional integrated-circuits to configure is stored within the computer at all times. it into a minimum system. It can execute about 200 instructions, taking up to 60 microseconds per instruc- Additional memory devices for storage of bulk data such tion. as patient data, test results for a 24 hour period or data to be uised as "ba-k-up" for information in use by The Intel 80)&O is another eight-bit microprocessor the computer. The popular bulk storage devices in device, introduced in 1973. It requires only five widespread use ore floppy-disks and cassettes. The additional circuit devices to configure a minimum cassettes are about the size of standard audio cassettes, system. It has a "vocabulary" of 244 instructions, but they are of higher quality. The floppy-disks are taking about 8.5 microseconds to execute the slowest also magnetic storage devices, using a piece of circular ones. magnetic material about 8" in diameter. Costs for cassette and floppy-disk systems cost from $1000 and up. The newest Intel devices are the 8085 and the 8748. These devices are also eight-bit microprocessors. The 8085 is an 8080-like device which is easy to use, Conclusion has a simplified electronic structure and has a "family" of compatible integrated-circuit devices. Microcomputers and other advances in hardware such as The 8748 might be considered a microcomputer since semiconductor sensors and analog/digital converters some memory is incorporated on the chip. This device have made a wide variety of simple, intelligent instru- is useful in control applications where little data ments available to us to simplify patient care and processing is required. medical testing. Often, however, the cost of a new instrument is high, not because an expensive computer Another 8080-type device is the Z80 microprocessor is built-in the device, but because the computer has chip available from ZiZog Corporation and Mlostek. enabled us to utilize a technique which may still This microprocessor device also requires about four require expensive testing equipment. It would have or five additional "support" chips, but it has some been prohibitively expensive to even consider the advantages over the 8080 and 8085 in some applications design of the instrument without the advent of the where data manipulation will be a major portion of the microcomputer. task. Microcomputers and microprocessors have become "catch- There are a variety of other microprocessor chips and words" of instrument designers, users and salesmen. microcomputer systems available. Some representative Often people consider that a microcomputer-based samples are listed below: device is better than a comparable one without such a device built into it. This is not necessarily the Eight-Bit Microprocessors case. Many hospitals and laboratories feel the Motorola 6800 prestige of owning expensive computer-based equipment. MOS Technology 6503 Instead of pooling resources, many local hospitals will Fairchild F-8 purchase their own equipment, thus forcing them to amortize the instrument's cost over fewer paitent tests. Twelve-Bit Microprocessors Devices such as "brain scanners" and "sonic scanners" Intersil 6100 (Compatible with Digital Equipment are typical examples. Corporation's PDP-8 software.) We must always remember that a computer or other instru- Sixteen-Bit Microprocessors ment should never be used to take the place of good, National Semiconductor PACE human judgement.

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