Why some memories have 3 chip enables instead of just having one?

[Anonymous]

Hello,

   

Why some memories have 3 chip enables instead of just having one? If all the chip enables must go to ground to be able to read or to write. What is the difference of having just one chip enable ?

[Anonymous · Accepted solution]

Multiple Chip selects are used when there are multiple components sharing the same Bus (address , data or Both) the chip selects are used  to decode or select one of the multiple components and deselect the others

       

Higher performance (read as frequency) products tend not to share Bus due to signal integrity limitations when extra loads are hanging on the Bus. These parts are typically used in Point to point connections as compared to the lower performance products where Multi-drop is OK.  As a result, higher performance products tend to have fewer or no chip selects