On Sat, Nov 12, 2022 at 11:59 AM Antonio Carlini via cctalk <cctalk@classiccmp.org> wrote: > > Surely a microcontroller is just a 555 with a few extra transistors?
For suitable (large) values of 'few'? Actually I can think of many differences... Firstly, the full equivalent circuit of the 555 is in the datasheet. So I can predict how it should behave under all conditions (there are many things you can do with a 555 besides astables and monostables). I have never seen an equivalent circuit, or a gate level description of a microcontroller. All 555s are the same. If it fails I can replace it. Microcontrollers cease to be the same once they are prgrammed. If a microcontroller fails then I'm stuck. I won't be able to get the firmware I would argue that 555s are a lot more reliable than microcontrollers. And have a much longer life than the time to bitrot of most microcontroller flash memories It's a lot easier to test a 555 than it is to test a microcontroller. 555s do not have illegal internal states they can get into. Microcontrollers almost always do. Hence the need for watchdog timers which IMHO are a kludge, > Another tool in the box, just that it happens to be very cheap. Cheap != good They have their uses. But like many tools they can be misused and often are. -tony