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Board NEDONAND-4

A project log for NEDONAND homebrew computer

NEDONAND is 8-bit homebrew computer entirely built out of many 74F00 chips (2-input NAND gates)

SHAOSSHAOS 02/25/2016 at 06:041 Comment

I extended a little 4-bit ALU circuit to give V (overflow) output only in case of add/subtract operations:

Eagle design implementing this called NEDONAND-4 (and it uses four NEDONAND-1 boards):

Pin descriptions:

1.1) GND - ground
1.2) D0 - output data bit 0
1.3) D1 - output data bit 1
1.4) D2 - output data bit 2
1.5) D3 - output data bit 3
1.6) COUT - output of carry/borrow
1.7) VOUT - output of overflow
1.8) /O0 - inverted O0 (just in case)
1.9) /O1 - inverted O1 (just in case)
1.10) /O2 - inverted O2 (just in case)
1.11) NC - not connected
1.12) VCC - power +5V

2.1) O0 - operation input bit 0
2.2) O1 - operation input bit 1
2.3) O2 - operation input bit 2
2.4) C - carry/borrow input
2.5) A0 - first argument bit 0
2.6) A1 - first argument bit 1
2.7) A2 - first argument bit 2
2.8) A3 - first argument bit 3
2.9) B0 - second argument bit 0
2.10) B1 - second argument bit 1
2.11) B2 - second argument bit 2
2.12) B3 - second argument bit 3

Board for NEDONAND-4 was already ordered on OSHPark:

P.S. This design was revised !!!

Discussions

SHAOS wrote 03/01/2016 at 09:13 point

This board is a little wrong - version from March 1st is better...

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