AL103 Revision 1.0
Table 16: VLAN Mapping for MAC Based Loading Trunk
PORT
BIT
1
1
1
1
1
1
1
0
1
1
1
1
1
1
0
1
1
1
1
1
1
0
1
1
1
1
1
1
0
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
Note: All bits are set to “1” except the ports themselves.
3.8 Flow Control
The AL103 can operate at two different modes, half- and full-duplex. Each port can operate at
either full- or half-duplex and can be configured to have flow control enabled or no flow control
independently on a per port basis.
3.8.1 Half Duplex Flow Control (Backpressure)
If the half-duplex flow control option is elected, backpressure will be used for flow control.
Whenever the receive frame buffer of a port is full, the MAC of the port will start sending a JAM
signal through the port. The remote station after sensing the JAM signal will defer transmission.
Backpressure flow control is applied to ensure that there is no dropped frame. The AL103 supports
two types of backpressure, collision based and carrier based.
Carrier based backpressure is generated by the AL103, when the switch port’s frame buffer is full.
The AL103 will cease to jam the line when the port has buffer space available for frame reception.
The IPG of the jamming signal can be selected from 48BT, 56BT, 65BT, 72BT, and 96BT. This can
be selected in register 02 bits 3 and 2. The BpIPGSelEn bit must be set to 1 to select backpressure
IPG less than 96BT.
Collision based backpressure is generated by the AL103, only when the switch port receives a
frame. The AL103 will cease to jam the line, when the line is idle.
The carrier based backpressure has several advantages over collision based backpressure such as:
9/00
Reference Only / Allayer Communications
25
ABC [ ABC Taiwan Electronics Corp ]
