How to define 2-port RAM output (old data or don't care)

[Altera_Forum]

Hello,  

does anyone know how to define 2-port RAM output(q) for read-during-write? I am using simple 2-port RAM(1 port with read and write) with separate read and write clock(wr_clk, rd_clk) and I just can't choose either old_data or don't care because the selection page was skipped by megawizard.. :(  any help would be much appreciated..   thanks!

[Altera_Forum]

Hi konyemko, 

 the "Read-During-Write" only makes sense when using the same clocks for read and write. When using separate clocks for both sides, you can not assume a relationship between the two clocks and therefore you can not select the "Read-During-Write" option in this case.   Hope this helps...

[Altera_Forum]

thanks Sanmao, i understand now. I have to choose single clock for read/write, then i can select either old_data or don't care for read-during-write. 

 thanks! :)