Atmel SpaceWire Router SpW-10X User Manual
Ref.: UoD_SpW-10X_
UserManual
Issue: 3.4
SpW-10X
SpaceWire Router
User Manual
Date: 11
th
July 2008
Preliminary
145
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.
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 SpW-10X routing
tables so that a packet arriving at a router with an invalid (unused) logical address will be spilt
immediately.
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 SpW-10X routing
tables so that a packet arriving at a router with an invalid (unused) logical address will be spilt
immediately.
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.
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 SpW-10X device is reset, part of a NULL pattern is present on
the serial data/strobe outputs of the running link when reset is released, see Figure 13-1. Data and
strobe outputs hold their previous values until reset is applied as seen in Figure 13-2. When reset is
the serial data/strobe outputs of the running link when reset is released, see Figure 13-1. Data and
strobe outputs hold their previous values until reset is applied as seen in Figure 13-2. When reset is