IP175A LF
Preliminary Data Sheet
27/60
February 20, 2006
Copyright © 2004, IC Plus Corp.
IP175A LF-DS-R08
4.7
VLAN
4.7.1
Port base VLAN
IP175A LF supports port base VLAN functions. It separates IP175A LF into some groups (VLAN). A port
is limited to communicate with other ports within the same group when the function is enabled. Frames
are limited in a VLAN group and will not transmit out of this VLAN group. A port can be assigned to one or
more VLAN groups. The members (ports) of a VLAN group are assigned by programming EEPROM
register 0Eh~12h of or MII register 13h~15h.
The VLAN function can be active even if there is no EEPROM. IP175A LF supports an easy way to
enable a sub set VLAN function without EEPROM.
A default configuration of VLAN is adopted if pin 113
(VLAN_on) is pulled high. The VLAN group in this mode is illustrated in the pin description of VLAN_on.
It is benefit in a router application that an individual LAN port can shares a WAN port. The setting in
register takes precedence of the setting on pins.
4.7.2
Tag / un-tag
IP175A LF supports tag / un-tag functions. When the function is enabled, IP175A LF inserts the
pre-defined tag into a forwarded frame if the frame is forwarded to a tagged field. IP175A LF strips the
tag of a frame if the frame is forwarded to an untagged field. The operation is illustrated as follows.
IP175A LF doesn’t support tag VLAN function.
The operation of a output port
Frame type of the
received packet
Forward to a untagged filed
Forward to a tagged field
Untagged
Transmit as received
1. Insert VLAN tag to the packet.
2. The inserted VLAN tag is defined in the
EEPROM register of source port.
Priority-tagged
(VLAN ID=0)
Strip tag
1. Keep priority field.
2. Modify the VLAN ID.
3. The modified VLAN tag is defined in the
EEPROM register of source port.
VLAN-tagged
Strip tag
Transmit as received
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