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SpaceWire Router |
| UserManual | |
Issue: | 3.4 | ||
User Manual | |||
Date: | 11th July 2008 | ||
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8.3.3 Group Adaptive Routing
The SpaceWire router routing table can be set up to support group adaptive routing of packets. Setting the routing table contents is described in section 9.3.
In group adaptive routing a set of output ports can be assigned to a logical address. When a packet arrives with the logical address the routing table is checked for the set of output ports which the packet can use. The routing control logic then checks the possible router output ports to determine if any of them are free and ready to use. As soon as one of the possible output ports associated with the logical address of the packet is free and ready to use then the packet is routed through that output port. If all the set of output ports which the logical address packet can use are free then the router chooses the lowest numerical output port number to route the packet.
Arbitration is performed on group adaptive routing packets as defined in section 8.3.2.
The following
8.3.3.1 Normal Group adaptive routing
In normal group adaptive routing the lowest numerical output port in the group that is ready to use is used to transfer the packet. This is illustrated in Figure
Address 76 – Routing table entry |
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Header Deletion disabled |
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Port 4 |
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Port 5 |
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Port 6 |
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1 |
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76 | 1 |
| 4 |
| 2 | R1 | 5 |
76 | 3 |
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Group adaptive routing packet with address 76 arrives at port 1 Group adaptive routing packet with address 76 arrives at port 3
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2 | R1 | 5 | 76 |
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Routing logic assigns port 4 to port 1
And port 5 to port 3
Figure 8-10 Normal group adaptive routing
8.3.3.2 Group adaptive routing when busy
The situation when some of the output ports in group are busy is illustrated in Figure
Preliminary | 92 |