Memory bits

Altera_Forum · ‎03-03-2007

Hi,

I am using a cyclone 1 FPGA chip having about 290,000 memory bits. After I finished my design and while compilation with quartus, I get get an error printing the following message :"Error: Selected device has 64 RAM location(s) of type M4K RAM. However, the current design needs more than 64 to successfully fit."

That's inspite the face that I have only used 180,000 memory bits which means I still got enough bits to use. What does that mean ?

Thanks in advance

Altera_Forum · ‎03-04-2007

Hi,

First: Have enabled SignalTap? It needs memory bits in order to save the states.

(It is a typical signal tap error)

Second: I am not sure if you can combine memory blocks from several columns into one large chunk.

I have never used cyc_I, so I am just guessing.

g

Altera_Forum · ‎03-07-2007

You can't count bits and determine how much more is available unless you are using all 9 bits of each byte. A 64x1 memory will consume all 4096+512 bits of an M4K just as a 512x9 will, but you only use 64 bits vs 4608, losing 4544 bits. If you are that tight on resource usage you will need to plan your design a bit more carefully. Remember that NIOS and JTAG UART with cache both use M4K as well as your added logic.