Doubt about it 6-to-64 decoder

[tnnelectro]

Hi,
I followed the attached diagram, the datasheet of 74HC137, to create a 6-to-64 decoder,

But I have a doubt:

The pin shown in the arrow, always connected to the STROBE signal?

http://obrazki.elektroda.pl/5079304200_1501508499.jpg

 

[dorke]

That line is connected to E2 .
It can be used as X6 if you need another address bit to create a 7 to128 decoder.
If unused, it should be connected to "1" constantly.

BTW,
you can used the 74154 to reduce the chip count.

 

[tnnelectro]

perfect,
But if I wanted to use the 74hc154 ... how would it be connected?

 

[dorke]

You would use four 74hc154 and one 139, for a total of 5 instead of 9 ICs.
What is this decoder for there may be other implementations.

 

[AnalogKid]

The #1 schematic is backwards from the traditional way of doing a staged address decoder. Usually the low order address bits to to all of the low level output generators, and the higher order address bits go to the pre-selector. #4 shows this.

ak

 

[tnnelectro]

Thanks great solution!

And if I wanted to do the opposite, that is 64-to-6?