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September 12, 2017 - IO's first bug ?

A project log for The Cardboard Computer - IO is my name

My goal is a 4-bit CPU using recycled cardboard substrate and Diode Transistor Logic. This is an educational platform for me.

dr-cockroachDr. Cockroach 09/12/2017 at 11:044 Comments

Well, IO is back to playing mind games or else it has its first hardware computer bug. I am seeing a garbage bit getting into the system and even with a slow clock speed, I can not keep track on where it is being introduced. Guess it is time to add a single step function  to the front panel. I had planned on adding it later but now I really could use it :-) With all the Leds I should be able to figure this out...

Ok now, it is September 16, 2017 and I think that I have squashed IO's first real bug. Found that in some buffers leading to the Accumulator there were 120k resistors that should have been 12k in the transistor collector path, Opps my bad :-)   I have been running IO with the 12k's for several hours without any problems. Folks out there need to be reminded that this is all new to me and now that goes for debugging :-)

September 17 and it has been 48 hours with IO running the accumulator and PC without any glitches, not one :-) Now I feel better about wiring up more circuits and working on the Brainwarp instruction set :-)

Discussions

Starhawk wrote 09/16/2017 at 21:48 point

Oy, that's an easy mistake. Remember your color codes! ...or do what I do, which is to use the calculator feature at hobby-hour.com/electronics/resistorcalculator.php -- it's super handy when your memory doesn't know how to memory ;)

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Dr. Cockroach wrote 09/16/2017 at 22:46 point

;-)

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EricH wrote 09/16/2017 at 02:21 point
Sounds like you might benefit from cardboard logic analyzer ;) but single-stepping should do...

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Dr. Cockroach wrote 09/17/2017 at 00:32 point

I would like to still do a logic analyzer as a tool for IO but that will have to wait for a while :-)

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