The FDIP28W (window ceramic frit-seal package) has a transparent lid which allows the user to expose the chip to ultraviolet light to erase the bit pattern. A new pattern can then be written to the device by following the programming procedure. For applications where the content is programmed only one time and erasure is not required, the M27C256B is offered in PDIP32, PLCC32 and TSOP28 (8 x 13.4 mm) packages.