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SpaceWire Router |
| UserManual | |
Issue: | 3.4 | ||
User Manual | |||
Date: | 11th July 2008 | ||
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WARNING
Packets can timeout and be spilled in a SpaceWire network without the destination receiving any notification of this. Packets with errors (e.g. parity error) can arrive at a destination terminated by an EEP. In a very special case it is also possible to receive an error free packet terminated by an EEP. It is important that the destination node is able to handle these cases.
WARNING
Care must be taken when setting a the routing tables to avoid a possible infinite loop. For example if there is a SpaceWire link made between two ports of a single router and a logical address routes a packet out of one of these ports then that packet will arrive back at the router, and be routed back out of the port again. Depending on the size of the packet it may block because it cannot get access to the output port the second time around as the tail of the packet is still being fed to the output port. In this case the blockage will cause a timeout (when watchdog timer mode set – see section 8.3.5) and the packet will be spilt. If the packet is a small packet it could continually circle around the loop. A SpaceWire network architecture and configuration should be checked for possible loops for all logical addresses being used. Unused logical addresses should NOT be configured in the
WARNING
If a SpaceWire port that is being used to configure a router has its transmit clock turned off then it will not be possible to configure the router using that port. Unless there is another connection with an active clock and which is not disabled that can be used to perform configuration the router will have to be reset before it can be configured again.
13.3 RESET ANOMALY
This section describes the reset anomaly and suggests appropriate workarounds.
13.3.1 Data Strobe Reset Waveform
If a SpaceWire link is running when the
Preliminary | 145 |
