Understanding EPROM Erasure and Package Types
If a microcontroller (MCU) does not have a quartz window, its EPROM cannot be erased and effectively functions as OTPROM (One-Time Programmable ROM). This is because the quartz window is essential for allowing ultraviolet (UV) light to erase the EPROM contents.
How to Identify Erasable EPROMs
You can determine whether an EPROM is erasable by checking the part number and package type:
If the package has a windowed ceramic dual in-line package the EPROM can be erase.
For example, on the HC05 family you can see this window being mentioned on the order numbers of the datasheet
