The PSnoop VHDL testbench module is used to examine and report on 9-bit SpaceWire data and is for the SpaceWire Switch Core (Router). The module can be used to monitor any interface that uses the same handshake mechanism as the Autonomous Cascadable Dual Port FIFO.


The report files that PSnoop generate can be used to check correct data flow and also perform latency calculations.

A typical PSnoop report file is shown below.

EDGE TIME	-	PACKET	-	BYTE	-	BINARY	-	DETAILS	-	UTILIZATION
80 ns	-	1	-	1	-	000000011	-	DATA 3	-	25% (1/4)
100 ns	-	1	-	2	-	011010110	-	DATA 214	-	40% (2/5)
120 ns	-	1	-	3	-	001011001	-	DATA 89	-	50% (3/6)
140 ns	-	1	-	4	-	010100101	-	DATA 165	-	57% (4/7)
160 ns	-	1	-	5	-	001010110	-	DATA 86	-	62% (5/8)
180 ns	-	1	-	6	-	010011001	-	DATA 153	-	66% (6/9)
180 ns	-	1	-	7	-	100000000	-	EOP	-	70% (7/10)
240 ns	-	2	-	1	-	000000011	-	DATA 3	-	66% (8/12)
340 ns	-	2	-	2	-	011001011	-	DATA 203	-	52% (9/17)
360 ns	-	2	-	3	-	011101100	-	DATA 236	-	55% (10/18)
380 ns	-	2	-	4	-	010110010	-	DATA 178	-	57% (11/19)
400 ns	-	2	-	5	-	100000001	-	EEP	-	60% (12/20)

The report file columns describe the following.

• Edge Time displays the time of the edge that the data is transferred on.
• Packet displays the packet number that the transferred data belongs to.
• Byte displays the byte number of the data within the packet.
• Binary displays the binary data being transferred.
• Details displays details of what the data being transferred is.
• Utilization displays the bandwidth utilization of the interface.