$25 worth of CMOS 4000 series IC's


Joined Feb 19, 2009

I've never heard of a microcontroller being programmed to act like a logic gate.

I have heard of and used of programmable logic gates, such as the GAL16 series, which were 16-20 pin devices that you could program with an EPROM programmer to act like any gate, or a combination of many gates in a single IC, with nS response time.

They were used very widely in industry as "black boxes" to prevent reverse engineering until CPLD devices were released.

Those little guys have evolved into the beloved FPGAs of today from Xilinx, etc, in which an entire CPU can be designed, though hundreds of I/O and other connections get a bit ugly to keep track of, outside of a demo board, they are not of much use to the hobbyist due to the cost of getting started.

The period between and after CPLD and FPGA is covered by Application Specific Integrated Circuits (ASIC), which are still built today for video cards, etc. The "program" is the masking of the silicon to do one task, and do it at lightning speed. Flash ADCs, Signal processing, etc.

microprocessors and microcontrollers can do many of the FPGA or ASIC functions, only at a mere fraction of the speed, which is why they exist.

Many hobby circuits that are programmed into a uC are actually state machines that would run faster in logic alone, no ALU and little RAM is needed. Simple games like Pong, Space Invaders, Breakout, etc can all be implemented in an logic, no CPU/ALU required.

Except nobody wants to wire-wrap a hundred ICs together to make a robot anymore. I still use wire-wrap a lot, but am very glad uCs exist to cut the number of external ICs down to a handful in non-time critical applications. This has made electronics a popular hobby again, so we should all be happy for it! :D