how to read data from FIFO in SOPC

hi，BadOmen or other gurus:

I write a SOPC component which is connected to AVALON bus.the custom component mainly consist of FIFO,I want to write a large bulk of datas in it and then read the datas out as the slave interface of the SOPC system.

in quartusII:

FIFO this_fifo(.aclr(~reset_n ),

. data(active_data),

.rdclk(clk_50M),

.rdreq(sl_read & sl_chipselect & out_en & (~rdempty) ),

.wrclk(clk_27M),

.wrreq(in_en & (~wrfull) ),

.q(sl_readdata),

.rdempty(rdempty),

.wrfull(wrfull)

);

In NiosII eclipse software,I write:

while(1)

{

read_fifo=IORD_ALTERA_AVALON_PIO_DATA(CUSTOM_FIFO_BASE);

}

return 0;

}

then I wacthed these signals by signaltapII,there are several phenomenons I cannot understand!~

1: There seems that the sl_chipselect,sl_read pulses are generated automatically,how can I control them,because I want to change the pulse frequences and the times when they need to be generated??

(I have try to add a timer in SOPC system and named it "sys_clk_timer",then in NiosII eclipse,I choose the "sys_clk_timer" ,but it cannot play a part)

2: I check the signaltapII waves ,and find that the active_data which is writed in FIFO are not the same as the sl_readdata which is readed from the FIFO(sometimes,the part datas in front of sl_readdata are right,then are wrong)??

3:I have readed the .pdf of the FIFO,it says that,"aclr" signal should controlled by wrclk,maybe the FIFO component I make is not stable??

thanks for your patient answer~

best regards!