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Diagnostics and Testability — Intel
®
82575EB Gigabit Ethernet Controller
324632-003 Intel
®
82575EB Gigabit Ethernet Controller
Revision: 2.1 Software Developer’s Manual and EEPROM Guide
January 2011 449
15.0 Diagnostics and Testability
15.1 Diagnostics
To assist in test and debug of device-driver software, a set of software-usable features have been
provided in the 82575. These features include controls for specific test-mode usage, as well as some
registers for verifying device internal state against what the device-driver might be expecting.
The 82575 provides software visibility (and controllability) into certain major internal data structures,
including all of the transmit & receive FIFO space. However, interlocks are not provided for any
operations, so diagnostic accesses may only be performed under very controlled circumstances.
The 82575 also provides software-controllable support for certain loopback modes, to allow a device-
driver to test transmit and receive flows to itself. Loopback modes can also be used to diagnose
communication problems and attempt to isolate the location of a break in the communications path.
15.1.1 FIFO Pointer Accessibility
The 82575's internal pointers into its transmit and receive data FIFOs are visible through the head and
tail diagnostic data FIFO registers listed in Section 13. Diagnostics software can read these FIFO
pointers to confirm expected hardware state following a sequence of operation(s). Diagnostic software
can further write to these pointers as a partial-step to verify expected FIFO contents following specific
operation, or to subsequently write data directly to the data FIFOs.
15.1.2 FIFO Data Accessibility
The 82575's internal transmit and receive data FIFOs contents are directly readable and writeable
through the PBM register. The specific locations read or written are determined by the values of the
FIFO pointers, which may be read and written. When accessing the actual FIFO data structures,
locations must be accessed as 32-bit words. See section 13.
15.1.3 Loopback Operations
Loopback operations are supported by the 82575 to assist with system and 82575 debug. Loopback
operations can be used to test transmit and receive aspects of software device drivers, as well as to
verify electrical integrity of the connections between the 82575 and the system (PCIe* bus
connections, etc.). Loopback operations are supported as follows:
Configuration for loopback operations vary depending on the link configuration being used.