ADM6926
Function Description
bytes each. The queues of each port are managed according to each port’s read/write
pointer.
Input buffers and output queues are maintained through proprietary patent pending
UNIQUE (Universal Queue management) scheme.
3.1.9
Half Duplex Flow Control
Back-pressure is supported for half-duplex operation.
When the ADM6926 cannot allocate a receive buffer for an incoming packet (buffer full),
the device will transmit a jam pattern on the port, thus forcing a collision.
3.1.10 Full Duplex Flow Control
When full duplex port runs out of its receive buffer, a PAUSE command will be issued
by ADM6926 to notice the packet sender to pause transmission. This frame based flow
control is totally compliant to IEEE 802.3x. When flow control hardware pin is set to
high during power on reset and per port PAUSE is enabled, ADM6926 will output and
accept 802.3x flow control packet.
3.1.11 Inter-Packet Gap (IPG)
IPG is the idle time between any two successive packets from the same port. The value is
9.6us for 10Mbps ETHERNET and 960ns for 100Mbps fast Ethernet.
3.1.12 Port VLAN or Tag VLAN Support
ADMtek Inc.
3-5
Two VLAN settings are supported by the ADM6926: the port-based VALN or the tag-
based VLAN. For the port-based VLAN the ADM6926 will use the port number as the
index to lookup the forwarding table. For the tag-based VLAN, the ADM6926 will use
the VID to lookup the forwarding table. Each port is assigned a Port VID as the Default
VID if tag-based VLAN is used. The ADM6926 will check TAG, remove TAG, insert
TAG, and re-calculate CRC if packet is changed:
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