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@1 +
Tx:@1 +
@3 +
Tx:@3 +
@1 [ | #01 #02 #03 EOP ]
Tx:@1 [ | #01 #02 #03 EOP ]
@3 [ | #07 #08 #09 EOP ]
Tx:@3 [ | #07 #08 #09 EOP ]
// Barrier lifted at T=1680.481 093 370 1s
Rx:@1 /*1680.481 093 388 0s*/ #01 #02 #03 /*1680.481 093 537 3s*/ EOP
Rx:@3 /*1680.481 093 386 7s*/ #07 #08 #09 /*1680.481 093 537 3s*/ EOP
The output from the
SpWIO
program shows that the reception of the two packets was synchronised to within
1.3 ns (the resolution of time-tags on the DSI), and that the propagation delay through the two cables, plus the
MSR buffers, was under 18 ns.
The MSR’s recording of this activity, as shown by
read.jar
is:
java -jar read.jar so-example.msr
//-4Links.READ (v18:20120504/v33:20110920)
//- so-example
ss ms us ns Flow Activity
1680.481 093 372 0s 1<--2 Data @0000 01 02 03
1<--2 EOP at 1680.481 093 522 7s (SOP + 0.151us) ˜159.3 Mb/s
1680.481 093 372 0s 7-->8 Data @0000 07 08 09
7-->8 EOP at 1680.481 093 521 3s (SOP + 0.149us) ˜160.8 Mb/s
1680.481 093 378 7s 7<--8 Data @0000 07 08 09
7<--8 EOP at 1680.481 093 528 0s (SOP + 0.149us) ˜160.8 Mb/s
1680.481 093 378 7s 1-->2 Data @0000 01 02 03
1-->2 EOP at 1680.481 093 529 3s (SOP + 0.151us) ˜159.4 Mb/s
This recording corroborates the measurements made by the DSI, above.
13
Option CO – Controlled Outputs
Using the CO option, it is possible to synchronise the transmission of any character in the transmit stream to an
external clock transition.
Low-to-high transitions on the rear-mounted SMA connector pair J1-J2 permit the transmission of traffic beyond
each HOLD character that is inserted into the transmission stream. The high logic threshold is approximately 1V.
See section 3.3, “SMA Synchronization Connectors”, for details of the DSI’s SMA synchronization connectors.
Each port on the DSI has a transmit buffer of approximately 32 kbytes, which stores data characters, EOP tokens
and HOLD markers. It is not possible to query the number of packets in this buffer.
Control is at the SpaceWire token level - the user chooses exactly where to delay the data stream until the next
SMA signal transition occurs, by inserting a HOLD marker at that point. HOLD markers may be inserted in the data
streams for multiple SpaceWire ports; the user is responsible for buffering sufficient SpaceWire traffic at each
port.
In the examples below, the DSI was synchronised via an ATI to an IRIG source, and the trigger signal was
generated at one pulse per second from the IRIG source. The DSI had a loopback connector on port 4, and the
port 4 transmit speed was 100Mb/s. The controlling software was
SpWIO
.