# Why an n to 2^n decoder needed

#### glitterized_dreamz

Joined Feb 13, 2007
6
I need a short answer for this question...Why is an "n to 2^n decoder needed for a memory using an n-bit address?

#### Dave

Joined Nov 17, 2003
6,970
Because thats how a decoder works, it converts a n-bit coded input, gives 2^n outputs where only one bit is set to 1 dependant on the input.

Dave

#### Ron H

Joined Apr 14, 2005
7,014
Because thats how a decoder works, it converts a n-bit coded input, gives 2^n outputs where only one bit is set to 1 dependant on the input.

Dave
Yes, but who ever heard of a memory that doesn't have binary-coded addressing, i.e., a memory with 1024 addressable locations would have a 10 bit address bus.
I'm thinking this is about a memory with multiple chips, all multiplexed onto the same data bus. The decoder is needed for the chip enables. For instance, if you had 8 chips, you would need a 3-to-8 line decoder.

#### Dave

Joined Nov 17, 2003
6,970
I'm thinking this is about a memory with multiple chips, all multiplexed onto the same data bus. The decoder is needed for the chip enables. For instance, if you had 8 chips, you would need a 3-to-8 line decoder.
This is pretty much what I was aiming at, however I could probably have made it clearer as to the application to memory devices - though I thought this would be clear to the OP from my original statement. Ultimately, the unique data word at the output of the decoder is utilised as the selection mechanism - i.e. providing an enable signal.

Dave