Realm confusion: Is it analog or digital?

Realm confusion: Is it analog or digital?
Analog 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.