PCIe DMA chaninig example

I simulated the chaining DMA example of PCI express,what I observed in simulation was the initially the "start of packet" & "end of packet signal" was high and were changing randomly for some time,then a data packet was sent,and again random data was observed

Can anybody explain what flow how the chaining dma example works

like

1.initilization phase.2....phase.3........phase