A long time ago in a valley far, far away, I worked for a company named SEEQ Technology. They had just developed a microcontroller call the SEEQ72720. It was a clone of the TI TMS7000.
It had 256 bytes of RAM, 2K of EEPROM main memory, 32 I/O pins, and ran on 5V at a whopping 8 MHZ. I think it consumed 100mA or or half a watt. All of this was on a die the size of your fingernail and housed a 40 pin ceramic DIP package.
We take features like in-circuit programming and self-updating storage for granted today. But development code was stored in a piggy-backed UV EPROM. Need to updated the code? Unplug the EPROM, burn a new one, pop the old one in a UV oven and it would be ready to go again... in 20 minutes.
When you thought you had it right, you programmed an OTP (one-time-programmable) part and tested it. (The EPROM parts sometimes behaved slightly differently) If testing found a bug or there was future change, the OTP when in the trash and the process started over again.
Intel started shipping parts with the UV EPROM built into the device. No more piggy-back packages with their bad connections and occasionally flaky behavior. But you still had to wait 20 minutes to UV erase the part.
What made the 72720 unique was the EEPROM memory. It could be erased and reprogrammed in a few seconds: pop it out of the socket, into the programmer, down-load new code and put it back in the circuit. It could be even be programmed using a 5V supply and a parallel port on a PC.
And it had massive I/O drivers. They could source 20mA, and sink 80mA. I built a multiplexed clock display using just (4) 7 segment LEDs and the SEEQ72720 driving them directly thru 8 series resistors. No buffers, no transistors.
SEEQ was never committed to the micro controller market and the 72720 never gained traction. A Google search turns up only a couple references to the 72720. SEEQ went on to develop flash technology as we know it today and the company was sold to National Semiconductor and National to TI. (A bit of irony there.)
Atmel and Microchip (and again TI) went on to dominate the world of embedded processors that had been pioneered by Intel (8048/8051), Motorola (68HC11) and National (COP-4, I believe the COP series is still made by TI.)
I took a detour into the world of graphics, PCs and 100W CPUs, but I never forgot the little 8 bit micro that started my interest in things embedded, where a little processor could actually make something happen in the real world.
Ultimately I found my way back to the embedded micro-controller world and have been working with embedded HW and SW for the last 3 years.
Would I trade today's faster processors, with more memory, JTAG debugging, in-system programming, optimizing C-compilers, and current sipping power consumption, for the processors and tools from the past? No way! They only make me appreciate what is available in the embedded world today.
-Mark
