The S29GL256P has word or byte mode addressing.
Pull the BYTE# pin to ground to address the device in byte mode
BYTE# Selects data bus width. At VIL, the device is in byte configuration and data I/O pins DQ0-DQ7 are active and DQ15/A-1 becomes the LSB address input. At VIH, the device is in word configuration and data I/O pins DQ0-DQ15 are active.
We recommend the S29GL512T is our latest family of devices which has byte or word programming instead of GL-P. It has the same pin mapping and foot print except for the BYTE # pin which is used to select to Byte or word configuration. As Paulo mentioned in the above response you can pull it to ground and use it in Byte mode.
Please refer the GL-T datasheet from the link given below :
You can also refer the migration application note form GL-S to GL-T from the link given below: