Atmel SpW-10X Operation with 5V Powered LVDS Devices, External Port Data Signals, User Manual

	SpW-10X	Ref.:	UoD_SpW-10X_
	SpaceWire Router		UserManual
		Issue:	3.4
	User Manual
		Date:	11th July 2008
5.2.3 Operation with 5V Powered LVDS Devices
	WARNING

Since LVDS is based on a current loop it should not matter what the supply voltage is to an LVDS device connected to the SpW-10X router. However, there is a potential problem when connecting to devices with power supplies greater than 3.3 V, which is the supply voltage of the SpW-10X device. It should be emphasised that during normal operation there is no problem, but if the LVDS device connected to the SpW-10X device can fail in such a way as to put a higher voltage than 3.3 V on to the pins of the SpW-10X device then this can cause a problem. The simplest way to overcome this potential problem is to ensure that the LVDS devices driving the SpW-10X device are all powered by 3.3V.

5.3 EXTERNAL PORT DATA SIGNALS

The External port signals are listed in Table 5-3. The timing of these signals is shown in Figure 6-1 External port write timing specification and Figure 6-2 External port read timing specification.

Table 5-3 External Port Interface Signals

PinNo	Signal	Dir	Description	Type
112	EXT9_OUT_DATA(8)	Out	Output data from external port number one	CMOS3V3
111	EXT9_OUT_DATA (7)		FIFO. Bit eight determines the type - data,
110	EXT9_OUT_DATA(6)		EOP or EEP. The encodings are defined as:
107	EXT9_OUT_DATA(5)
104	EXT9_OUT_DATA(4)		(8)(7......0) – Bits
103	EXT9_OUT_DATA(3)		(0)(dddddddd) - Data byte
102	EXT9_OUT_DATA(2)		(1)(XXXXXXX0) - EOP.
101	EXT9_OUT_DATA(1)
			(1)(XXXXXXX1) - EEP.
100	EXT9_OUT_DATA(0)
			Bit 7 is the most significant bit of the data byte.
113	EXT9_OUT_EMPTY_N	Out	FIFO ready signal for external output port	CMOS3V3
			zero. When high the FIFO has data. When low
			the FIFO is empty.
114	EXT9_OUT_READ_N	In	Asserted (low) to read from the external output	CMOS3V3
			port zero FIFO.
			A pull-up resistor (e.g. 4k7 Ω) should be
			connected to this input if External FIFO port 9
			is not being used.
123	EXT9_IN_DATA(8)	In	Input data to external port number one FIFO.	CMOS3V3
122	EXT9_IN_DATA(7)		Bit eight determines the type - data, eop or
121	EXT9_IN_DATA(6)		eep. The encodings are defined as:
			Preliminary	37