Hi
I was given the task of designing a simple 4 bit ALU which just has the two functions 'A plus B' and 'A minus B'. The design was only supposed to use full adders, multiplexers and inverters.
The circuit I came up with can be seen here:
http://i43.tinypic.com/2lg6t.jpg
I think it will work (?) but I was unsure if there is a better way of doing it without using 4 multiplexers (one for each of the input bits).
Also I was wondering if the order of inputs to a multiplexer matters? is there a correct way of ordering the inputs? In my circuit, I have input the inverted bit as the first input to each multiplexer and the original bit as the second input. I also said that when S = 1, this specified the subtraction function (so the inverted bit should be selected).. is it correct to say that when the control bit is 1 the top input to the 2 bit multiplexer will be selected?
thanks for any advice
I was given the task of designing a simple 4 bit ALU which just has the two functions 'A plus B' and 'A minus B'. The design was only supposed to use full adders, multiplexers and inverters.
The circuit I came up with can be seen here:
http://i43.tinypic.com/2lg6t.jpg
I think it will work (?) but I was unsure if there is a better way of doing it without using 4 multiplexers (one for each of the input bits).
Also I was wondering if the order of inputs to a multiplexer matters? is there a correct way of ordering the inputs? In my circuit, I have input the inverted bit as the first input to each multiplexer and the original bit as the second input. I also said that when S = 1, this specified the subtraction function (so the inverted bit should be selected).. is it correct to say that when the control bit is 1 the top input to the 2 bit multiplexer will be selected?
thanks for any advice