the simulation result of PCIE DMA simple example

hello everybody:

recently I did some simulation in modelsim-altera6.5 according to AN532 downloaded from altera.com.First I built an sopc system including DMA Control,On Chip memory(RAM) and PCI Express.My quartus version is 9.1.Then I run the testbentch provided in the project folder.The result is in the attachement.

I don't understand why the value of DMA signal "length" is always"000000",and the simulation result is also run out of control,Can anyone figure out the reason?