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IP175A LF
Preliminary Data Sheet
26/60
February 20, 2006
Copyright © 2004, IC Plus Corp.
IP175A LF-DS-R08
4.6
CoS
IP175A LF supports two type of Cos. One is port base priority function and the other is frame base
priority function. IP175A LF supports two levels of priority queues. A high priority packet will be queued in
the memory as a high priority queue, this action will ensure more bandwidth for the high priority packets
in the transmission.
The packets received from high priority port will be handled as high priority frames if the port base priority
is enabled. It is enabled by programming the corresponding bit in EEPROM register 0Eh~12h of or MII
register 13h~15h. Each port of IP175A LF can be configured as a high priority port individually.
IP175A LF examines the specific bits of VLAN tag and TCP/IP TOS for priority frames if the frame base
priority is enabled. The packets will be handled as high priority frames if the value of VLAN tag or TCP/IP
TOS field meets the high priority requirement. It is enabled by programming the corresponding bit in
EEPROM register 16H~21H or MII register 17h~1Ch. The frame base priority function of each port can
be enabled individually.
The Cos function can be active even if there is no EEPROM. IP175A LF supports an easy way to enable
a sub set CoS function without EEPROM. Port 4 can be set as a high priority port if pin 64 (p4_high) is
pulled high. Frame base priority function of all ports is enabled if pin 63 (Cos_en) is pulled high. The
setting in register takes precedence of the setting on pins.
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