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AEROFLEX GAISLER
62
RT-SPW-ROUTER
Copyright Aeroflex Gaisler AB
June 2012, Version 1.2
the link interface to enter the error-reset state. Disconnections are handled in the link-interface part in
the tx clock domain because no receiver clock is available when disconnected.
Received characters are flagged to the host domain and the data is presented in parallel form. L-Chars
are the handled automatically by the host domain link-interface part while all N-Chars are stored in
the receiver FIFO for further handling. If two or more consecutive EOPs/EEPs are received all but the
first are discarded.
4.2.5
Time interface
The time interface is used for sending Time-codes over the SpaceWire network and consists of a
timein signal, timectrlin signal, tickin signal, timeout signal, timectrlout signal and a tickout signal.
Each Time-code sent from the core is a concatenation of the timectrlin and the timein signal. It is
transmitted each time tickin is kept asserted until the tickin_done output is asserted. Time-codes are
only transmitted when the link-interface FSM is in run-state and when the previous character trans-
mission is finished. This can cause a delay between when the assertion of tickin_done after tickin has
been asserted. If tickin is not kept asserted until tickin_done is asserted the time-code will not be
transmitted. Figure 14 shows an example of how a time-code is transmitted.
Received Time-codes are presented on the timectrlout and timectrl signals. They are valid when the
tickout output is asserted. A tickout is generated each time a valid time-code is received. When the
tickout is generated the tick-out signal will be asserted one clock-cycle. Figure 15 shows how time-
codes are received.
Receiver Clock Domain
Host Clock Domain
Receiver
D
DV
Got Time-code
Got FCT
Got NChar
Time-code[7:0]
NChar[7:0]
Got EEP
Got EOP
Figure 13. Schematic of the link interface receiver.
Figure 14. Transmitting a time-code using tickin, timein and timectrlin.
timein
tickin
clk
T0
tickin_done
timectrlin
C0