Atmel SpW-10X user manual TIME-CODE Interface Operation, External port read timing specification

SpW-10X	Ref.:	UoD_SpW-10X_
SpaceWire Router		UserManual
	Issue:	3.4
User Manual
	Date:	11th July 2008

CLK EXT_OUT_READ_Nx

EXT_OUT_DATAx

EXT_OUT_EMPTY_Nx

1	2	3	4
		DATA1
			read

5	6	7	8	9	10	11	12
	DATA2		DATA3				DATA4
		read				read

Figure 6-2 External port read timing specification

Reading of the External port is illustrated in Figure 6-2. When data is available in the External port FIFO then it is placed on the EXT_OUT_DATA bus and the EXT_OUT_EMPTY_N signal is asserted to signal to the external system that data is available. This is done synchronously to the SYSCLK signal (e.g. clock cycle 2 in Figure 6-2). When it is ready the external system asserts the EXT_OUT_READ_N signal synchronously with the SYSCLK signal (e.g. clock cycle 3) and the data is then read out of the external port on the next rising edge of the SYSCLK (e.g. start of clock cycle 4). If there is no more data available in the FIFO then the EXT_OUT_EMPTY_N is de-asserted once the data has been read. If the FIFO contains more data to transfer then the EXT_OUT_EMPTY_N remains asserted, the new data is placed on the EXT_OUT_DATA bus and the external system can read it as soon as it is ready. The read access is ignored if there is no data available (EXT_OUT_EMPTY_N is active).

6.2 TIME-CODE INTERFACE OPERATION

In this section the time-code interface operation is defined.

EXT_TICK_IN

SEL_EXT_TIME

EXT_TIME_IN

Time-code inputs

EXT_TIME_IN

used for time-code

Internal time-code

counter

used for time-code

Figure 6-3 Time-Code Input Interface

Time-codes can be generated by the router on request of the external system to which it is attached. A time-code is generated whenever the router detects a rising edge on the EXT_TICK_IN signal as illustrated in Figure 6-3. The value of the time-code to be transmitted is either taken from the inputs or from the time-code counter inside the router. The time-code source used depends on the value of the

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