Corp. SpaceWire Router User Manual

Ref.:
UoD_SpW-10X_
UserManual
Issue:
3.4
SpW-10X
SpaceWire Router
User Manual
Date:
11
th
July 2008
Preliminary
135
10.6.5 Time-code Jitter
The variation in time to propagate a time-code through a routing switch.
Time-code jitter occurs in the synchronisation handshaking circuits and the transmitter where the
maximum delay time the time-code has to wait to be transmitted is one data character. The jitter is
measured as
()()
TXPERIODSYSPERIODTCJIT TTT ×
+
×= 52
10.6.6 200M bits/s Input and Output Bit Rate Example
The following table defines the latency and jitter measurements when the transmit bit rate and receive
bit rate are 200M bits/s.
Table 10-6 SpaceWire Router Latency and Jitter Measurements (Bit rate = 200Mbits/s
Description Symbol Value Units
Switching Latency T
SWITCH
133.3 ns, max
Router Latency – SpaceWire to SpaceWire port T
SSDATA
546.6 ns, max
Router Latency – SpaceWire to External port T
SEDATA
316.6 ns, max
Router Latency – External to SpaceWire port T
ESDATA
363.3 ns, max
Router Latency – External to External port T
EEDATA
166.6 ns, max
Time-code Latency – SpaceWire to SpaceWire port T
SSTC
409.3 ns, max
Time-code Latency – SpaceWire to External port T
SETC
316.6 ns, max
Time-code Latency – External to SpaceWire port T
ESTC
359.9 ns, max
Time-code Jitter T
TCJIT
116.6 ns, max
[1] Note all figures are worst case