4 Bit ALU

5 Nov 2016

This is my 4 bit test ALU.

It has 6 functions, Add with carry, Subtract with carry, Shift Right with carry fill, AND, OR, and XOR.

While assembling the ALU I made some errors two of them being with the adder carry chain being wired backwards (MSB to LSB)

And the same with the shifter; wired to left shift instead of right shift.

It uses 181 transistor's and I am currently constructing the full 8 bit ALU which will contain 346 transistor's.

A photograph with labels:

The small Mux is to select the carry out from ether the adder, shifter, or the carry In.

The inverter mux selects between invert or pass (used to select subtraction/addition).

Tim

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dougw over 8 years ago

Those cards look like they have headers suitable for wire-wrapping, potentially reducing the number of breadboards you need....
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timswift over 8 years ago in reply to dougw

I am currently planing on soldering (and wiring) sockets on to a large proto-board and pluging the cards into these.
Wire-wrapping just seems like it would be difficult (I've never used it).

Tim
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phoenixcomm over 8 years ago in reply to timswift

timswift ts a piece of cake! You just have to have the right tools, and wire for that matter. Don't try and wire wrap without a wire wrap gun. You just have to practice a few times. Wire: 30 AWG (very common) silver-plated copper wire with Kynar insulation. I use 26AWG, it works better in this application, and last you need a Wire Stripper Cutter.: either of the two below will work. I have both types and I like the little one as you can set the length of the strip. Please DO NOT use any other type of wire stripper as they will invariably nick your wire. Oh yes also a good manual wire unwrapping tool as well.. Most of the time you can pick the tools up on ebay.

Here is a video "How To" https://www.youtube.com/watch?v=IXvEDM-m9CE and here are some pictures which will helpful: DISCRETE WIRING - SOLDERLESS WRAPPED ELECTRICAL CONNECTIONS - WIRE WRAP
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timswift over 8 years ago in reply to phoenixcomm

In order to use wire-wrap with my "SIP" boards I think I will have to use stackable pin headers soldered on to a proto-board.
I want to be able to replace boards if necessary (desoldering transistors is not my favorite past time).

Tim
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timswift over 8 years ago in reply to phoenixcomm

In order to use wire-wrap with my "SIP" boards I think I will have to use stackable pin headers soldered on to a proto-board.
I want to be able to replace boards if necessary (desoldering transistors is not my favorite past time).

Tim
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phoenixcomm over 8 years ago in reply to timswift
No, no reason to solder the wrap will hold it in place, but maybe solder a power and power ground, not logic ground..
you can take a look at how I built an interface.
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