Internals of a microcontroller.

I just though I would share this with you guys. I was playing around with some old microprocessors and microcontrollers today when I removed a label off of a Motorola MC68HC11 8-bit Microcontroller (only works with assembly codeing) and found a neat little viewing window of the chip packaging.

I dont know if any of you have taken classes in materials processing or micoprocessor, but its neat to see the actual stuff you learned in real life.

Heres the closeup, it also looks like AMD fab'd this for Motorola.





The last photo was the best of them all so I sharpened it and worked on clarifying the image.

What you see is a circular viewing window with the square silicon substrate underneath it. The star shaped lines are actually high purity aluminum that have been microsolderd onto the chip surface to contact pads. One wire for each pin of the DIP package. The white stuff underneath the square is a type of ceramic glue they use to insulate and prevent shifting.

This kind of jogged my memory on these subjects and I was wondering if you think an article on silicon chip manufacturing and how they make cpus would be enjoyed on the overclockers.com website? If you think so, Ill get to work on it.

Yeah why not?

Wierd that a microcontroller has a viewing window - what you gonna do, poke it with a pin?

Yup, its really cool.

Everyone likes pics:

Intel 4004


Intel 8008

Wierd that a microcontroller has a viewing window

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Not at all. I've seen more then a few.

So you think people would get a kick out of that? Of course, I would throw in some semi heavy transport phenomena physics, a little smeiconductors 101 to explain how the substrates work and such.

I know most peole around these circles have seen pictures and have an idea on how these things work and how theyre made, but most people just have the wrong facts or dont have a clue.

I heard one guy say they that a cpu is a piece of silicon they fold millions of times. Sorry bud.

Photolithography is a fun process.

Although when we studied this we went oldschool. We actually made laboratory diodes, LED's and bipolar transistors in the materials lab. We did the doping by hand and annealed with and oven. Then nickel electro-plated. Was kinda neat.

L337 M33P said:

Wierd that a microcontroller has a viewing window - what you gonna do, poke it with a pin?

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Some programmable controllers can be erased by shining UV light onto parts of the chip. I think the MC68HC11 just has a EEPROM, so there wouldn't be any need to expose the die. But maybe someone had a few million DIPs to get rid of...

I reprogrammed quite a few of these old chips this summer. I would first erase them by putting them under a UV light for about 45 minutes or so, then place them into a programmer. Then, I would copy the software from another microcontroller and write it to the blank one. Finally, I covered the little window up with the software revision and customer name.

We used these microcontrollers as our CPU's for our control module that runs harvester-mounted tomato sorting machines.

It was all really quite fascinating.

Yeah it has 512byte EEPROM, 256bytes RAM and 8KB ROM. Thats why I was so surprised it had a a window. Ive actually never come across the volatile memory. Im just a youngin. This 68HC11 is old enough as it is.

georgelogy said:

I reprogrammed quite a few of these old chips this summer. I would first erase them by putting them under a UV light for about 45 minutes or so, then place them into a programmer. Then, I would copy the software from another microcontroller and write it to the blank one. Finally, I covered the little window up with the software revision and customer name.

We used these microcontrollers as our CPU's for our control module that runs harvester-mounted tomato sorting machines.

It was all really quite fascinating.

Click to expand...

I was wondering how you actually break the initerconnects of those kinds of PLD's when programming them. Is it a special piece of equipment that does it for you physically, or is it electrically induced?

Fushyuguru said:

So you think people would get a kick out of that? Of course, I would throw in some semi heavy transport phenomena physics, a little smeiconductors 101 to explain how the substrates work and such.

I know most peole around these circles have seen pictures and have an idea on how these things work and how theyre made, but most people just have the wrong facts or dont have a clue.

I heard one guy say they that a cpu is a piece of silicon they fold millions of times. Sorry bud.

Photolithography is a fun process.

Although when we studied this we went oldschool. We actually made laboratory diodes, LED's and bipolar transistors in the materials lab. We did the doping by hand and annealed with and oven. Then nickel electro-plated. Was kinda neat.

Click to expand...

I'd love to see such an article.

Fushyuguru said:

I was wondering how you actually break the initerconnects of those kinds of PLD's when programming them. Is it a special piece of equipment that does it for you physically, or is it electrically induced?

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It is Electronically Reprogrammable. I believe the UV light erases the volatile SRAM and then you plug it into a special programmer device that "burns" the new information into it. So basically, you can "give" the processor new instructions.

georgelogy said:

It is Electronically Reprogrammable. I believe the UV light erases the volatile SRAM and then you plug it into a special programmer device that "burns" the new information into it. So basically, you can "give" the processor new instructions.

Click to expand...

Yeah we studied these things. They have AND gates (with enables) that run in a grid with OR gates for outputs. When you put UV light on the grid, all of the connections are healed so the entire grid shorts out everywhere. Then you have to break connections to get the actual functions to go where and do what you want. We never found out how the interconnects are broken. So I guess the machine does it like you said, electrically, somehow.

Go for it Fushy, I want to see more!!!

cheers
Charlie

I find this all very interesting. Where can I find information on these microcontrollers? It would be fun to learn about them! I have way too much free time...

Here is a datasheet on one of these micro controllers. You can read all about them!

LINK

CamH said:

I find this all very interesting. Where can I find information on these microcontrollers? It would be fun to learn about them! I have way too much free time...

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a quick googleage can probably find you out some good info. but beyond that it would probably take a semester course in college.