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298 Software Developer’s Manual
Register Descriptions
BAM 15 0b
Broadcast Accept Mode.
0 = ignore broadcast; 1 = accept broadcast packets.
When set, passes and does not filter out all received broadcast
packets. Otherwise, the Ethernet controller accepts, or rejects a
broadcast packet only if it matches through perfect or imperfect
filters.
BSIZE 17:16 0b
Receive Buffer Size
Controls the size of the receive buffers, allowing the software to
trade off between system performance and storage space. Small
buffers maximize memory efficiency at the cost of multiple
descriptors for bigger packets.
RCTL.BSEX = 0b:
00b = 2048 Bytes.
01b = 1024 Bytes.
10b = 512 Bytes.
1b1 = 256 Bytes.
RCTL.BSEX = 1b:
00b = Reserved; software should not program this value.
01b = 16384 Bytes.
10b = 8192 Bytes.
11b = 4096 Bytes.
VFE 18 0b
VLAN Filter Enable
1
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. RCTL.VFE determines
whether the VLAN filter table participates in the packet acceptance
criteria. RCTL.CFIEN and RCTL.CFI are used to decide whether
the CFI bit found in the 802.1Q packet’s tag 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 RCTL.CFIEN 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.
Reads as 0b.
DPF 22 0b
Discard Pause Frames
0 = incoming pause frames subject to filter comparison.
1 = incoming pause frames are filtered out even if they match filter
registers.
DPF controls the DMA function of flow control PAUSE packets
addressed to the station address (RAH/L[0]). If a packet is a valid
flow control packet and is addressed to the station’s address, it is
not transferred to host memory if RCTL.DPF = 1b. However, it is
transferred when DPF is set to 0b.
Field Bit(s)
Initial
Value
Description