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The application test

A project log for Self Clocking ROM

There are a few projects that can be implemented with a ROM and need a clock source...

rue-mohrRue Mohr 01/21/2023 at 01:392 Comments

My original application idea was a silly 4 bit to base 10, 7 segment display system, so I'll build that...

I made a new ROM image, I'll add the source as "main2.c" and "output2.bin"

In my original idea, I wanted to use a trick where one display is common anode, and the other is common cathode. With the commons connected together, you can only operate 1 display at a time, which is great for 2 display multiplexing.... BUT...

I didn't have a good set of displays in my collection to do this with (I searched for hours) so, I'd have to settle for adding a transistor to drive the second display.  :-/

Furthermore, loading the "oscillator" like this caused a large error in the duty. Duty error in something like this causes one display to be brighter than the other, so I added a few bias parts to bring it closer to 50%. AT 50% (if you adjust it such) the operation of the oscillator is not stable, it may stall or not start up with power, serves me for not adding another chip (74xx541) to drive the LEDs (its not good form to make a chip like this EEPROM try to drive LEDs)

I was not sure if all the bit timing would work ok here. When you address a location on a memory like this, not all the bits arrive at the outputs at the same time, which could cause "segment smudge"

But it was all ok, and kinda just worked!

kinda anti-climactic... (like fishing, and having your fish jump into the boat and knock itself unconscious on the seat when it lands, before you have managed to bait the hook and put the line into the water... but don't sit there looking at the worm, row back to shore and cook the fish!)

BUT! the possibilities of what can be done are AWESOME...

Discussions

zpekic wrote 04/10/2023 at 03:59 point

Clever idea! Btw, you may be looking for this one :-) https://digilent.com/shop/pmod-ssd-seven-segment-display/

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Rue Mohr wrote 04/10/2023 at 19:52 point

cool! but OUCH! $7? :S

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