Programmer’s Guide BCM5722
10/15/07
Broadcom Corporation
Document 5722-PG101-R Ethernet MAC Control Registers Page 254
TRANSMIT MAC LENGTHS REGISTER (OFFSET 0X464)
This register contains various length fields that control the operation of the transmit MAC.
RECEIVE MAC MODE REGISTER (OFFSET 0X468)
Table 206: Transmit MAC Lengths Register (Offset 0x464)
Bit Field Description Init Access
31:14 Reserved – 0 RO
13:12 IPG CRS Length When multiplied by 2, this field indicates the number of
bytes from the end of the interpacket gap (IPG) during
which incoming carrier is ignored. The IEEE recommends
ignoring carrier during the last 1/3 of the IPG.
00 R/W
11:8 IPG Length When multiplied by 2, this field indicates the number of
bytes in the entire IPG.
0h R/W
7:0 Slot Time Length When multiplied by 2, this field indicates the number of
bytes in the slot time.
00h R/W
Table 207: Receive MAC Mode Register (Offset 0x468)
Bit Field Description Init Access
31:27 Reserved – 0 RO
26 enable_rx_res_ethernet
(BCM5906 only)
Setting this bit enables RX residential Ethernet support. 0 R/W
25 ipv4_fragment_fix
(BCM5906 only)
Setting this bit enables a checksum calculation fix for IPv4
fragment packet
0R/W
Reserved (all others) – 0 RO
24 IPv6_parsing_enable (BCM5722,
BCM5755, BCM5755M,
BCM5756M, BCM5757 only)
• 1 = Enable IPv6 RX which includes IPv6 packet parsing,
checksum offload and IPv6 RSS
• 0 = Disable IPv6 RX
0R/W
Reserved (other devices) – 0 RO
23 RSS_enable (BCM5722, BCM5755,
BCM5755M, BCM5756M, BCM5757
only)
• 1 = Enable RSS function.
• 0 = Disable RSS function. FHDE will ignore the
RSS_valid from Frame Cracker and set RSS_valid to be
0 in frame descriptor of each packet.
If RSS is enabled, but no RSS hash types are enabled, it’s
the same as RSS disabled. If RSS_enable is 0, but some
hash types are enabled, it’s the same as RSS disabled.
When RSS_enable is set to 1, at least one of the RSS hash
types should be enabled. Any combinations of hash types
are supported.
0R/W
Reserved (other devices) – 0 RO
22:20 RSS Hash Mask Bits (BCM5722,
BCM5755, BCM5755M,
BCM5756M, BCM5757 only)
These bits specify the number of hash bits that are used to
offset into the indirection table. A value of one specifies
that only bit 0 of the hash is used to offset into the
indirection table (so only the first two entries of the table
are utilized.) A value of seven specifies that bits 6:0 of the
hash are used to offset into the indirection table. A value of
zero will result in undefined behavior and should not be
programmed.
0x7 R/W
Reserved (other devices) 0x0 RO
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