# In Regards to a 4WayMux16 and 8WayMux16...

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## In Regards to a 4WayMux16 and 8WayMux16...

 I am writing because I need some tips on creating a 4WayMux16. It turns out that as progress the "contracts" with the Mux gates are becoming complex in the sense of me not being able to add together the contracts. I created a Mux16 of which carries one sel. Then a two way mux 16 carries two sel's. So how do I add a 4 way mux being the numbers keep adding up unevenly. the contract for a mux4way16 is 2 BUT a mux 8 way 16 is 3 sel's? This is confusing nothing is adding up. Please help.
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## Re: In Regards to a 4WayMux16 and 8WayMux16...

 Administrator A 2 way Mux 16 only has a single select input. Look at section 1.2.3 more closely. The number of available options (input channels in the case of a multiplexer or output channels in the case of a demultiplexer) is 2^n where n is the number of select bits. If you have: 1 select bit, you have 2^1 = 2 channels. 2 select bit, you have 2^2 = 4 channels. 3 select bit, you have 2^3 = 8 channels. 4 select bit, you have 2^4 = 16 channels. etc.
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## Re: In Regards to a 4WayMux16 and 8WayMux16...

 So what you are saying is that when I create a logic gate that has 4 16 bit inputs the numbers of the Sel's can be represented somehow with 00, 01, 10, and 11? So more or less I get 4 Sel's to work with? Because it looks like that I only get to Sel's to work with because in the Contract of the Mux4Way16 it says IN sel[2] of the interface. Like this shows? /**  * 4-way 16-bit multiplexor:  * out = a if sel == 00  *       b if sel == 01  *       c if sel == 10  *       d if sel == 11  */
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## Re: In Regards to a 4WayMux16 and 8WayMux16...

 Administrator Your 4-way mux has two select bits. With two select bits you can support four channels numbered, as you indicated, {00, 01, 10, 11}.