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Processor Circuit Diagram

Fascheue

New Member
I just finished taking an embedded systems course that was mainly centered around software. We used an ARM processor throughout the semester and our professor drew a simplified circuit diagram of a processor. I’ve attached the picture below. Because the course was software focused, we didn’t go beyond a quick explanation of how this simplified processor would work.

What additional components would a complete version of this circuit contain?

Also, wouldn’t the demultiplexer output 0 to all outputs except for the selected register (Rd) in this diagram? Is some of the logic excluded for simplicity, or am I misunderstanding something?
 

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dr pepper

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Not really my best area, however the arduino due uses a version of the arm that doesnt need much extra to run, the board has a voltage reg and a usb to serial converter thats about it, and you could depending on what device you were buiding even make a board without those.
A microcontroller usually has everything on board to run software, rom, ram, gpio, serial etc.
 

Nigel Goodwin

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Not really my best area, however the arduino due uses a version of the arm that doesnt need much extra to run, the board has a voltage reg and a usb to serial converter thats about it, and you could depending on what device you were buiding even make a board without those.
A microcontroller usually has everything on board to run software, rom, ram, gpio, serial etc.
The Arduino doesn't use an ARM processor. Although MicroChip/Atmel do manufacturer ARM processors under licence.

The tiny part of circuit in the OP seems pretty meaningless, it's not a 'simplified' processor, but merely a tiny part of one.

For the OP - I would completely ignore the 'diagram', it's of no use to you (or anyone else), and presumably was only given to explain a small specific point.
 

Fascheue

New Member
The Arduino doesn't use an ARM processor. Although MicroChip/Atmel do manufacturer ARM processors under licence.

The tiny part of circuit in the OP seems pretty meaningless, it's not a 'simplified' processor, but merely a tiny part of one.

For the OP - I would completely ignore the 'diagram', it's of no use to you (or anyone else), and presumably was only given to explain a small specific point.
It was drawn to demonstrate how a processor performs actions based on machine code. If this is only a tiny part of a processor, what are the remaining parts? The diagram contains a register, control unit, and ALU. Maybe I’m mistaken, but I thought that those were the necessary parts of a processor.
 

kubeek

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Most Helpful Member
Also, wouldn’t the demultiplexer output 0 to all outputs except for the selected register (Rd) in this diagram? Is some of the logic excluded for simplicity, or am I misunderstanding something?
If you call it a demux then it should, but in reality each register has an Write Enable signal, that allows the contents to be overwritten. The data lines go to all the registers in parallel, and the WE signal is then given to the appropriate one which writes the data where it belongs.
 

be80be

Well-Known Member
The Arduino Nano 33 IoT is based on the SAMD21 microcontroller
MicrocontrollerSAMD21 Cortex®-M0+ 32bit low power ARM MCU


Nigel Goodwin Hate to break it to you but Arduino uses Arm Microcontrollers
It's not just AVR anymore.

They have more ARM in there line up then AVR
There is about 12 ARM arduino boards

And about 6 AVR cored arduinos
 

ChrisP58

Well-Known Member
Not really my best area, however the arduino due uses a version of the arm that doesnt need much extra to run, the board has a voltage reg and a usb to serial converter thats about it, and you could depending on what device you were buiding even make a board without those.
A microcontroller usually has everything on board to run software, rom, ram, gpio, serial etc.
The Arduino doesn't use an ARM processor. Although MicroChip/Atmel do manufacturer ARM processors under licence.
The Arduino DUE does use a 32-bit ARM core microcontroller.
https://store.arduino.cc/usa/due
 

unclejed613

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gophert

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OK, the VAST majority of Arduinos out there don't use ARM processors! :D
On average, people know the answers to standard questions and come here for unusual cases/less obvious problems. No credit for answers that only cover "the VAST majority" of cases.
 

dr pepper

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Was the first processor a 404 or something, 4 bits 100khz, that sounds easier to understand.
 

rjenkinsgb

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Was the first processor a 404 or something, 4 bits 100khz, that sounds easier to understand.
The Intel 4040 was the first microprocessor - all the main functions in a single IC

There were many non-integrated CPUs and computers prior to that, starting with electromechanical ones in the 1930s

eg. The image below the block diagram of the processor section of a PDP-8 computer, very sophisticated for its time but also simple enough to have been built with all discrete components.
It is a bit fuzzy I'm afraid, its a screen grab of a scanned page image from this site, which also contains a lot of other information and background that may be useful to the OP.

pdp8_processor.jpg
 

dr pepper

Well-Known Member
Most Helpful Member
The earliest chip I've played with is the 8080a, well into the microprocessor times.
I have a couple of dekatrons similar to the harwell witch computer project.
 

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