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Realm confusion: Is it analog or digital?








EE Times


Stephan OhrAnalog Devices product marketer Tremont Miao had a problem when he first talked to us about his company's "Microverter." Is this an 80C51 microcontroller with a really good analog front end? Or is this a 12-bit A/D converter so sophisticated that a microcontroller was part of its feature set? A visit to the recent Embedded Systems Conference reminded me that this kind of "realm confusion" is very common.

Philips Semiconductors' 80C51 microcontroller has on-chip A/D and D/A converters, as does National Semiconductor's Cops series controllers and Microchip Technology's PIC series. Anacon System's VSAC1000 ac motor servo has an 8-bit A/D converter, a custom microprocessor, a pulse-width modulator and power MOSFETs to drive the motor coils. Motor speed and torque are user-programmable. Is the expertise to design and run one of these things primarily analog or digital?

Microcontroller parts resemble analog circuits in the kind of get-your-fingers-dirty design skills needed to make these things work. If you sit with an applications developer, you see wires going every which way. Instead of scope, you see a logic analyzer.

When I was at Signetics nearly 20 years ago, I was involved in developing applications notes and conference papers on data converters-mostly motor controllers and servos-that included 8048s (forerunner to the 8051). It was an analog applications engineer who designed the motor-control servo, teaching himself enough control code to get the 8048 servo to slide into various positions.

One of the companies I called on, Rowe International in Grand Rapids, Mich., was the leader in coin changers. The early dollar-bill changer they fashioned for the state's airports was smart enough to tell Canadian from American dollars, and to issue coins in either currency. The system consisted of a simple optical scanner, 8-bit A/D converter and 8048 with a lookup table.

Rowe's early coin changers used weights and pulleys Rube Goldberg-style to identify a mystery coin and plunk out the change. At Embedded Systems, Miao showed a Rube Goldberg machine of his own. The Microverter-controlled line would pick up a ball and send it on its way through an elaborate chain of wire-mesh pulleys, elevators, conveyors and chutes. Even at 8 bits, quipped Miao, the controller would have enough cycles to sort the balls by colors.










The views and opinions expressed in this column are strictly those of the author and should not be taken as an editorial position of EE Times or any of its other editors, publications or Web sites.


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