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Software Developer’s Manual 301
Register Descriptions
MPE 4 0b
Multicast Promiscuous Enabled
0b = Disabled.
1b = Enabled.
When set, passes without filtering out all received multicast packets.
Otherwise, the Ethernet controller accepts or rejects a multicast
packet based on its 4096-bit vector multicast filtering table.
LPE 5 0b
Long Packet Reception Enable
0b = Disabled.
1b = Enabled.
LPE controls whether long packet reception is permitted. When LPE
is cleared, the Ethernet controller discards packets longer than
1522 bytes. When LPE is set, the Ethernet controller discards
packets that are longer than 16384 bytes.
For the 82541xx and 82547GI/EI, packets larger than 2 KB require
full duplex operation.
LBM 7:6 0b
Loopback mode.
Controls the loopback mode of the Ethernet controller.
00b = No loopback.
01b = Undefined.
10b = Undefined.
11b = PHY or external SerDes loopback.
All loopback modes are only allowed when the Ethernet controller is
configured for full-duplex operation. Receive data from transmit
data looped back internally to the SerDes or internal PHY. In TBI
mode (82544GC/EI), the EWRAP signal is asserted.
Note: The 82540EP/EM, 82541xx, and 82547GI/EI do not support
SerDes functionality.
RDMTS 9:8 0b
Receive Descriptor Minimum Threshold Size
The corresponding interrupt ICR.RXDMT0 is set each time the
fractional number of free descriptors becomes equal to RDMTS.
The following table lists which fractional values correspond to
RDMTS values. The size of the total receiver circular descriptor
buffer is set by RDLEN. See Section 13.4.27 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 0b
Reserved
Should be written with 0b to ensure future compatibility.
Reads as 0b.
MO 13:12 0b
Multicast Offset
The Ethernet controller is capable of filtering multicast packets
based on 4096-bit vector multicast filtering table. The MO
determines which bits of the incoming multicast address are used in
looking up the 4096-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
Should be written with 0 to ensure future compatibility
Reads as 0
Field Bit(s)
Initial
Value
Description