SPI EEPROM Routines

[dkinzer]

The attached file contains routines for reading/writing an external SPI EEPROM. Currently, the code only supports byte-writeable EEPROMs like the AT25256A and M95512. For devices that only support page writes, the code would need to be modified to perform a read-modify-write operation when data needs to be written to a portion of a page.

This code may be useful for those using the ZX-24n which has an otherwise unused AT25256A EEPROM onboard as well as in other applications that include such an EEPROM.