Re: teaching: from chip function to implementation

Posted by Todun on Apr 06, 2010; 11:16pm
URL: http://nand2tetris-questions-and-answers-forum.52.s1.nabble.com/teaching-from-chip-function-to-implementation-tp34534p701684.html

In a multi-output world, you will have the output section of your truth table show the number of outputs you have; just as you will have the input section of your truth table showing the number of inputs. Lets say we build a chip with 2-inputs and 4-outputs. We will do the canonical routine and determine when the outputs will be one and zero for each set of inputs. Afterwards, we will select the sets of inputs that give the "high" output(if that is what you want) then write out separate canonical forms for each output like so(high output case):

in1|in2||||out1|out2|out3|out4
0   0         0     0      0     1
0   1         0     0      1     0
1   0         0     1      0     0
1   1         1     0      0     0

out1=in1*in2
out2=in1*not(in2)
out3=not(in1)*in2
out4=not(in1)*not(in2)

Hope that helps.