IP175C/IP175C LF/IP175CH/IP175CH LF
Data Sheet
49/111
Mar 09, 2007
Copyright © 2004, IC Plus Corp.
IP175C/IP175CH-DS-R14
2.11
Special tag
IP175C/IP175CH supports special tag function to exchange switching information with CPU without
involving VLAN tag information. The special tag function is enabled by programming MII register 30.16.7
STAG_EN.
2.11.1
From CPU to switch
When special tag function is enabled, IP175C/IP175CH forwards packets from MII0 (CPU) by checking
special tag added by CPU. The tag definition is shown in the following table. IP175C/IP175CH will
remove the special tag 81XX and re-calculate CRC when it forwards the packet to a un-tag field.
IP175C/IP175CH will update the special tag to 8100 and re-calculate CRC when it forwards the packet to
a tag field.
Preamble
SFD
DA
SA
81XX(special tag)
Data
CRC
Special tag 81XX
Bit[15:12]
bit[11:8]
bit[7:5]
bit[4:0]
8
1
3’b0
00001: instruct 175C forwards the packet to port 0
00010: instruct 175C forwards the packet to port 1
00100: instruct 175C forwards the packet to port 2
01000: instruct 175C forwards the packet to port 3
10000: instruct 175C forwards the packet to port 4
2.11.2
From switch to CPU
When special tag function is enabled, IP175C/IP175CH sends packets to MII0 (CPU) with source port
information by adding special tag to the frame. IP175C/IP175CH will add the special tag 81XX and
re-calculate CRC when it receives the packet from a un-tag field. IP175C/IP175CH will update the tag
8100 to 81XX and re-calculate CRC when it receives the packet from a tag field. The tag definition is
shown in the following table.
Special tag 81XX
Bit[15:12]
bit[11:8]
bit[7:5]
bit[4:0]
8
1
3’b0
00001: the source port of the packet is port 0
00010: the source port of the packet is port 1
00100: the source port of the packet is port 2
01000: the source port of the packet is port 3
10000: the source port of the packet is port 4
Chinese ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
