IP175C/IP175C LF/IP175CH/IP175CH LF
Data Sheet
34/111
Mar 09, 2007
Copyright © 2004, IC Plus Corp.
IP175C/IP175CH-DS-R14
2
Functional Description
2.1
Flow control
IP175C/IP175CH supports the standard 802.3X flow control frames on both transmit and receive sides.
On the receive side, if IP175C/IP175CH receives a pause control frame, the IP175C/IP175CH will defer
transmitting next normal frame; on the transmit side, IP175C/IP175CH issues pause control frame (Pause
On, time slot count = 0xffff) to remote station when the output queue of the destination port is higher than
high water mark threshold. When the output queue of the destination port is lower than low water mark
threshold, IP175C/IP175CH issues pause control frame (Pause Off, time slot count = 0) to restart transmition.
Besides, IP175C/IP175CH provides an additional protect function, when it issues continuous 16 times of
Pause ON frame (network abnormal), no more Pause ON frame will be send.
When CoS is enabled, IP175C/IP175CH may disable the flow control function for a short term to
guarantee the bandwidth of high priority packets. A port disables its flow control function for 2 ~ 3
seconds when it receives a high priority packet. It doesn’t transmit pause frame or jam pattern during the
period but it still responses to pause frame or jam pattern.
2.2
Broadcast storm protection
A port of IP175C/IP175CH begins to drops broadcast packets if the received broadcast packets are more
than the threshold defined in MII register 30.11[15:14] or EEPROM register 59[7:6] bq_stm_thr_sel [1:0] in
10ms (100Mbps) or 100ms (10Mbps)
The function can be enabled by pulling high pin 102 BF_STM_EN or programming MII register 29.18.11.
2.3
Port locking (Port security)
IP175C/IP175CH supports port locking. Each port can be configured individually by programming MII
register 30.10[5:0] or EEPROM 57[5:0]. User has to reset IP175C/IP175CH to disable the function by
writing 16’h175C to MII register 30.0 after enabling this function. IP175C/IP175CH locks first MAC
address if the function is enabled. Any packet with MAC address not equal to the locked one will be
dropped. The aging function is recommended to be disabled, if port locking is enabled.
2.4
Port base VLAN
IP175C/IP175CH supports port base VLAN functions. It separates IP175C/IP175CH into some groups
(VLAN). A port is limited to communicate with other ports within the same group when the function is
enabled. Frames will be limited in a VLAN group and will not be forwarded 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 14~18 or MII register 19~21.
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