Atmel SpW-10X Manuel D’Utilisation

Ref.:   UoD_SpW-10X_ 

 

Issue:  3.4 

  

 

Date:  11

 

 

96

 

In blocking allowed mode the network path is blocked until the destination node starts to accept data 
again. Packets waiting to use the network path will wait indefinitely. 

In watchdog timer mode the router will timeout and the network path will be cleared so other packets 
can use the path. 

What happens when Blocking Allowed mode is being used and a destination node becomes blocked 
is illustrated in Figure 8-14 to Figure 8-16.  In this example two routing switches, R1 and R2, are 
connected to form a network and only SpaceWire ports 1 to 6 are shown for clarity. 

a)  A packet arrives at port 3 of routing switch R1 destined for port 4 and then port 5 of R2 (as 

shown by the path address 4, 5 at the head of the packet. 

R1

1

2

3

4

5

6

(a)

4

5

R2

1

4

2

3

5

6

 

b)  The packet is routed towards its destination but during packet transfer the destination stalls 

and does not accept any more data. The network path is blocked and the packet waiting at R1 
port 2 is also blocked 

R1

1

2

3

4

5

6

(b)

R2

1

4

2

3

5

6

4

4

 

c)  The path between routing switch R1 port 4 and routing switch R2 port 1 is now blocked. While 

the first packet is routed another packet arrives at port 2 on router R1 with destination port 4 
on router R1 and destination port 4 on router R2. The packet must wait as the ports are 
currently busy and can only be routed if the downstream node starts receiving data again.