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Intel
®
82575EB Gigabit Ethernet Controller — Receive Control Register - RCTL (00100h; R/W)
Intel
®
82575EB Gigabit Ethernet Controller 324632-003
Software Developer’s Manual and EEPROM Guide Revision: 2.1
352 January 2011
Field Bit(s)
Initial
Value
Description
Reserved 0 0b Reserved
Write to 0b for future compatibility.
RXEN 1 0b Receiver Enable
The receiver is enabled when this bit is set to 1b. Writing this bit to 0b stops reception
after receipt of any in progress packet. All subsequent packets are then immediately
dropped until this bit is set to 1b.
SBP 2 0b Store Bad Packets
0b = do not store.
1b = store bad packets.
This bit controls the MAC receive behavior. A packet is required to pass the address (or
normal) filtering before the SBP bit becomes effective. If SBP = 0b, then all packets
with layer 1 or 2 errors are rejected. The appropriate statistic would be incremented. If
SBP = 1b, then these packets are received (and transferred to host memory). The
receive descriptor error field (RDESC.ERRORS) should have the corresponding bit(s) set
to signal the software device driver that the packet is erred. In some operating systems
the software device driver passes this information to the protocol stack. In either case,
if a packet only has layer 3+ errors, such as IP or TCP checksum errors, and passes
other filters, the packet is always received (layer 3+ errors are not used as a packet
filter).
Note: Symbol errors before the SFD are ignored. Any packet must have a valid SFD
(RX_DV with no RX_ER in 10/100/1000BASE-T mode) in order to be recognized by the
82575 (even bad packets). Also, erred packets are not routed to the MNG even if this
bit is set.
UPE 3 0b Unicast Promiscuous Enabled
0b = Disabled.
1b = Enabled.
MPE 4 0b Multicast Promiscuous Enabled
0b = Disabled.
1b = Enabled.
LPE 5 0b Long Packet Reception Enable
0b = Disabled.
1b = Enabled.
LPE controls whether long packet reception is permitted. Hardware discards long
packets if LPE is 0b. A long packet is one longer than 1522 bytes. If LPE is 1b, the
maximum packet size that the 82575 can receive is 16383 bytes.
LBM 7:6 00b Loopback mode.
Controls the loopback mode of the 82575.
00b = Normal operation (or PHY loopback in 10/100/1000BASE-T mode).
01b = MAC loopback (test mode).
10b = Undefined.
11b = Loopback via internal SerDes (SerDes/SGMII mode only).
When using the internal PHY, LBM should remain set to 00b and the PHY instead
configured for loopback through the MDIO interface.
Note: PHY devices require programming for loopback operation using MDIO accesses.