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Receive Control Register - RCTL (00100h; R/W) — Intel
®
82575EB Gigabit Ethernet Controller
324632-003 Intel
®
82575EB Gigabit Ethernet Controller
Revision: 2.1 Software Developer’s Manual and EEPROM Guide
January 2011 353
RDMTS 9:8 00b Receive Descriptor Minimum Threshold Size
The corresponding interrupt is set each time the fractional number of free descriptors
becomes equal to RDMTS.
RDMTS[1:0] determines the threshold value for free receive descriptors. See
Section 14.3.41 for details regarding RDLEN.
00b = Free buffer threshold is set to 1/2 of RDLEN.
01b = Free buffer threshold is set to 1/4 of RDLEN.
10b = Free buffer threshold is set to 1/8 of RDLEN.
11b = Reserved.
Reserved 11:10 00b Reserved
Set to 0b for compatibility.
MO 13:12 00b Multicast Offset
Determines which bits of the incoming multicast address are used in looking up the bit
vector.
00b = bits [47:36] of received destination multicast address.
01b = bits [46:35] of received destination multicast address.
10b = bits [45:34] of received destination multicast address.
11b = bits [43:32] of received destination multicast address.
Reserved 14 0b Reserved
BAM 15 0b Broadcast Accept Mode.
0b = Ignore broadcast (unless it matches through exact or imperfect filters).
1b = Accept broadcast packets.
BSIZE 17:16 00b Receive Buffer Size
BSIZE controls the size of the receive buffers and permits software to trade-off
descriptor performance versus required storage space. Buffers that are 2048 bytes
require only one descriptor per receive packet maximizing descriptor efficiency.
00b = 2048 Bytes.
01b = 1024 Bytes.
10b = 512 Bytes.
11b = 256 Bytes.
Note: BSIZE is not modified when RXEN is set to 1b.
VFE 18 0b VLAN Filter Enable
0b = Disabled (filter table does not decide packet acceptance).
1b = Enabled (filter table decides packet acceptance for 802.1Q packets).
Three bits control the VLAN filter table. The first determines whether the table
participates in the packet acceptance criteria. The next two are used to decide whether
the CFI bit found in the 802.1Q packet should be used as part of the acceptance
criteria.
CFIEN 19 0b Canonical Form Indicator Enable
0b = Disabled (CFI bit found in received 802.1Q packet’s tag is not compared to decide
packet acceptance).
1b = Enabled (CFI bit found in received 802.1Q packet’s tag must match RCTL.CFI to
accept 802.1Q type packet.
CFI 20 0b Canonical Form Indicator bit value
If CFI is set, then 802.1Q packets with CFI equal to this field is accepted; otherwise,
the 802.1Q packet is discarded.
Reserved 21 0b Reserved
Should be written with 0b to ensure future compatibility.
Field Bit(s)
Initial
Value
Description