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392 Software Developer’s Manual
Appendix (82540EP/EM and 82545GM/EM Differences)
Note: Though the 82540EP/EM supports devices with up to 512 KB of memory, smaller devices may
also be used. Accesses to memory beyond the FLASH device size results in access wrapping as
only the lower address bits are utilized by the FLASH.
The
82540EP/EM does not provide an interface for performing an “Erase” operation to the serial
Flash device. Flash write operations must be performed to an initialized or pre-erased Flash device.
If in-circuit erase is required, an external source (such as hardware's software-definable pins) can
be used to drive the Flash pins to perform the erase operation.
B.2.2 No TBI/Internal SerDes Interface
The 82540EP/EM does not support a TBI/internal Serdes interface. As a result, all TBI/internal
SerDes-related registers (for example, RXCW) should not be used.
B.2.3 Single-Port Functionality
The 82540EP/EM and the 82545GM/EM do not have the dual-port functionality of the
82546GB/EB. As a result, the 82540EP/EM and the 82545GM/EM appear as single PCI bus
devices.
B.2.4 32-Bit PCI Support
No developer impact.