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124 Software Developer’s Manual
EEPROM Interface
5.7 Parallel FLASH Memory
All Ethernet controllers except the 82540EP/EM provide an external parallel interface to an
optional FLASH or boot EEPROM device. Accesses to the FLASH memory are controlled by the
Ethernet controllers, but are accessible to host software as normal PCI reads or writes to the
FLASH memory mapping range. Software developers can also map FLASH memory to I/O space.
The Ethernet controllers support 8-bit wide parallel FLASH memory up to 4 Mb (512 KB); an
appropriate size for typical applications would be 1 Mb (128 KB). The size of the FLASH
implemented in the design can be encoded into bits in the EEPROM. FLASH and expansion ROM
base address registers are reconfigured based on these EEPROM settings.
Representative FLASH memory devices that have been found to work satisfactorily with the
Ethernet controllers are listed in Table 5-22:
The FLASH memory interface trace routing is not critical because the interface runs at a very slow
speed. In a tightly space-constrained design, the FLASH memory device is a good choice for
placement in relative isolation from the Ethernet controllers.
Note: The 82540EP/EM provides an external interface to a serial FLASH or Boot EEPROM device. See
Appendix B for more information.
Table 5-22. FLASH Memory Manufacturers
Manufacturer
Manufacturer’s Part
Number
Atmel
AT49LV010
AT49BV002AN-70J1
Silicon Storage
Technology
SST39V512
39VF020-90-4I-NH
39VF020-70-4C-NH