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  • Author Author: dougw
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Who remembers EPROM?

dougw

This is just an off the wall way to say thank you to element14 and Xilinx. They had a little give-away draw to win a Zynq book and they ended up sending me a huge book called Exploring Zynq MPSoC and a screw driver set. I also recently completed a Project14 so I threw in some images from that project.

This is a digital microscope image of a 27512 EPROM. It took a lot of digging in my archives to find this chip, but I wanted a chip with a ready-made window so the microscope could image the actual silicon.

image

Click on the image for a full size view.

Here is what a typical EPROM looks like with its window to allow UV light to erase the memory:

image

I also took a a closer image just to see what this microscope can do....

image

I'm having a lot of fun with this microscope.

 

Here is a video of the FPGA Technology Quiz prizes and the Pi HQ Camera microscope in action....

 

I once used EPROM without a CPU as a look up table to convert 18 bit gray code to binary.

Have you ever tried to use sunlight to erase an EPROM?

Feel free to add your EPROM stories below, I'm sure there are lots of them.

 

Relevant Links:

FPGA Technology Quiz

I Spy With My Digital Eye .... a Pico PI

Parents

  • We used UV eraseable eproms to store configuration data for the computer peripherals that we designed.

     

    I found my old UV eraser in with a bunch of old computer stuff.

    image

     

    I also found a sample box of ST parts circa late 80s.

    imageimage

     

    These were byte wide, so 4kx8 and 32kx8.  I must have used the 1 Meg eprom somewhere image.

    image

  • in reply to ralphjy

    I still have one, I repurposed it to make UV light photographs.

     

    DAB

  • in reply to DAB

    I always wanted a UV light to erase EPROMs, at least until EPROMs stopped being used.

    I wonder if UV light would erase EEPROM (or FLASH which is a type of EEPROM)

  • in reply to dougw

    My guess would be that the metallization on the surface is too dense with a Flash part (presumably the UV parts were deliberately designed with a clear area above much of the storage well for the light to get in), but I could be wrong.

     

    BTW thanks for the pictures. The one that shows clearly the welds of the bond wires is particularly nice. You can see, from the variation in the placement of the tack point, why they needed the landing pads the size they were.

  • in reply to dougw

    This is an explanation of the gate from the 1975 Intel Memory Design Handbook. This applies to the early parts like the 1702 and the 2704.

     

    image

     

    I was wrong to talk of a 'well' as it's really a floating gate formed above the substate within a grown insulating oxide layer, not sunk into it. Charge gets onto the gate by avalanching, so it's different to a Flash memory where the mechanism is tunneling. The diagram shows that the space above the gate is kept clear of metal to allow UV light to get to the charge on the floating gate.

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  • in reply to dougw

    This is an explanation of the gate from the 1975 Intel Memory Design Handbook. This applies to the early parts like the 1702 and the 2704.

     

    image

     

    I was wrong to talk of a 'well' as it's really a floating gate formed above the substate within a grown insulating oxide layer, not sunk into it. Charge gets onto the gate by avalanching, so it's different to a Flash memory where the mechanism is tunneling. The diagram shows that the space above the gate is kept clear of metal to allow UV light to get to the charge on the floating gate.

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