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SpaceWire Router |
| UserManual | |
Issue: | 3.4 | ||
User Manual | |||
Date: | 11th July 2008 | ||
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Figure 8-19 Destination Node Blocked: Watchdog Mode (c)
d)The packet waiting at routing switch R1 port 2 is routed and the network blockage is cleared. Routing switch R2 port 5 still has data waiting to be sent followed by the end of packet, therefore packets routed to port 5 will again cause a blockage which will be cleared again in the same manner until the fault is detected by a higher level protocol.
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2 | R1 | 5 | 2 | R2 | 5 |
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(d).
Figure 8-20 Destination Node Blocked: Watchdog Mode (d)
8.3.5.2 Stalled source
A source of a SpaceWire packet can stall for some reason and stop sending data part way through sending a packet. A router will see this situation as an input port which has stalled, no longer sending data part way through sending a packet although the SpaceWire link is still running. This situation can occur due to an error in the network or in the node that was providing data.
In blocking allowed mode the network path will be blocked until the source node supplies the end of packet. Other packets waiting to use the network path will wait indefinitely.
In watchdog timer mode the routers will timeout and the network path will be cleared so other packets can use the path.
Blocking Allowed
The sequence of events when a source is stalled and Blocking Allowed mode is being used is illustrated in Figure
a)A packet arrives at routing switch port 3 with destination address 4, 5 which will route to routing switch R2 port 5. Another packet arrives which is destined for routing switch R2 port 4.
Preliminary | 98 |