Atmel SpaceWire Router SpW-10X User Manual

Ref.:   UoD_SpW-10X_ 

 

Issue:  3.4 

  

 

Date:  11

 

 

98

 

1

2

3

4

5

6

(c)

1

4

2

3

5

6

4

4

EEP

R1

R2

 

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. 

R1

1

2

3

4

5

6

(d).

1

4

2

3

5

6

R2

 

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. 

The sequence of events when a source is stalled and Blocking Allowed mode is being used is 
illustrated in Figure 8-21 to Figure 8-24. 

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.