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The data bus width can be selected by the user.
When the BYTE# pin is pulled LOW, the device will work in byte mode where DQ7-DQ0 will remain active.
Where as, when the BYTE# pin is pulled HIGH, the device will work in word mode where DQ15-DQ0 remain active.
You can find a description of the BYTE# pin in Table 28. I/O Summary.
Here is the link to the datasheet - http://www.cypress.com/file/218336/download
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