column enable (CAS; CE)

An enable signal that on some dynamic RAMs actuates only the column-oriented internal circuits and the data input/output circuits. Most devices normally require the RAS signal to be present for the CAS signal to be effective. In some newer designs, however, special sequences of the RAS and CAS signals are used to actuate certain special device control functions. For devices that have one CAS per output, the CASs are numbered beginning with 0. For two-byte devices that have one CAS per byte, the CASs are designated LCAS and UCAS. LCAS affects DQ0-DQ7, and UCAS affects DQ8-DQ15. For devices that have more than two bytes and one CAS per byte and for all modules that have one CAS per byte, the CASs are numbered beginning with 0. CAS0 affects DQ0-DQ7, CAS1 affects DQ8-DQ15, CAS2 affects DQ16-DQ23, and CAS3 affects DQ24-DQ31.

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