psmart
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PS I agree with everything you just said.
jib
Just 'shop' which Dragon should understand! So to explain:-
In the old days, digital circuits were built up with building blocks, ie. logic gates contained within a package (chip). These were generically called the 74' series (made with standard transistors) or the 4000 series (made with CMOS FETS - Field Effect Transistors). You would design your circuit using these building blocks and transfer it onto a PCB (circuit board).
As you can imagine, a complicated circuit would take lots of space, so as silicon density increased, you got PLA's (Programmable Logic Arrays) which were a single 'chip' but had 1000's of logic gates inside. You designed the circuit using the 'array' of gates in the PLA, created a fuse map and hard programmed it so that your PLA became a circuit which accomplished a task. More recently, like Flash RAMS (memory which you can electrically re-program), PLA's had a memory which stored the program (fuse map) so you could reprogram them on-site if your circuit was buggy, or you could reprogram them to perform a completely different task, all whilst the finished product was in the hands of your client.
uC or micro-controllers are dedicated computers on a chip, with hard memory (Flash RAM), working memory (RAM), and dedicated Input/Output subsystems such as control lines, CAN controller etc. They also contain protected memory for storing serial numbers etc.
Ive attached some photos of a 270cdi ECU internals, the uController is circled in yellow, the injector drivers are in red, the Flash-RAM used for the engine management program is in Blue.
The reason why Im certain that you will have a PLA or uController in a MUX (not having disected a MUX) is that RS-232 is a serial transmission system (takes a number, converts it to binary, packages it up, the 1 bit at a time sends it to the receiver) which is slow and cannot for example emulate CAN transmissions/reception which contains an order of magnitude higher speed and data is assembled in packets, much like a LAN packet.