Quartus warning

I was trying to use the SDRAM controller without using the NIOS. I am now using the vhdl file generated from SOPC builder.

Things are great during simulation i.e. However, when I try to synthesize it. I receive the following warning message:

Warning: Can't pack node sdram_0:sdram_con_inst|m_addr[10] to I/O pin.

+Warning: Can't pack logic cell sdram_0:sdram_con_inst|m_addr[10] and I/O node zs_addr[10] -- logic cell cannot be packed as I/O register +Warning: Can't pack logic cell sdram_0:sdram_con_inst|m_addr[10] and I/O node sdram_0:sdram_con_inst|m_addr[10] -- logic cell cannot be packed as I/O register +Warning: Can't pack logic cell sdram_0:sdram_con_inst|m_addr[10] and I/O node sdram_0:sdram_con_inst|i~28445 -- logic cell cannot be packed as I/O register

The m_addr[10] ties to the address pin of the RAM. Bits 9 and 8 are the same as well. Can't seem to find out the reason.

I understand that a register is inserted at the pins to optimize timing. If this this node is not packed, does it mean to say that it is bypassed to the pin. In a sentence, how does this impact functionality?

Timing analyzer tests indicate that +ve slack so in the end, timing seems up to scratch.

Thanks for your help! ;->

Ted

Ted,

Warnings like this normally come from the fitter, and indicate that an assignment (generally a FAST_INPUT_REGISTER or FAST_OUTPUT_REGISTER assignment) that requested that a register be placed in an IO cell could not be honoured.

You should check the sub-messages around this message (by clicking on the "+" to expand the sub-messages, if you're running in the GUI) and right click on the messages to get on-line help on why the register couldn't go in the IO cell.

If you met all your timing constraints anyway, the design will still work fine. Putting the registers in the IO cell is purely a performance optimization to improve IO timing. You should make sure that the timing constraints are complete though (i.e. you have timing constraints on everything you care about), since the timing analyzer only analyzes what you ask it to.

Vaughn Altera