The Second chip enable on the some of our Cypress SRAM's does not provide any additional functionality. The primary purpose of having two chip enable pins is to allow memory banking. If you are using the part without any depth/width expansion then you should make sure to have both the chip enables active. If you want to use the part for depth/width expansion then you can take advantage of two chip enable pins by disabling one memory when the other is active. The part will operate only if you have /CE1=low and CE2=High, if either one is disabled the part becomes inactive.