Re: Problem reading RAM.

Altera_Forum · ‎04-30-2017

I have a state machine


when ST_MCP25625_TO_RAM_2  =>
    if (idx1 < MAILBOX_COUNT-1) then
        temp_mailbox_addr := (MAILBOX_SIZE * idx1) + MAILBOX_OFFSET;
        ram_addr_a <= std_logic_vector(to_unsigned(temp_mailbox_addr, 10)); --load start address
        idx2 := 0; 
        RamState <= ST_MCP25625_TO_RAM_3;
  else   --mailbox not found
      RamState <= ST_RAM_IDLE;
 end if;
 
when ST_MCP25625_TO_RAM_3 =>
    if (idx2 < 4) then
        tmp_mailbox(idx2) <= slave_data_out1;
        if (to_integer(unsigned(ram_addr_a)) < RAM_SIZE) then
            ram_addr_a <= ram_addr_a + 1; 
        end if;          
        idx2 := idx2 + 1;
  else
      mailbox_id := tmp_mailbox(3) & tmp_mailbox(2) & tmp_mailbox(1) & tmp_mailbox(0);
      RamState <= ST_MCP25625_TO_RAM_4;                                                        
end if;

Initially temp_mailbox_addr = 2

And RAM initialized

address - data

2 - 5

3 - 6

4 - 7

5 - 8

But after ST_MCP25625_TO_RAM_3 I read

tmp_mailbox(0) = 0

tmp_mailbox(1) = 5

tmp_mailbox(2) = 6

tmp_mailbox(3) = 7

So it seems like a tact is missing to update ram_addr_a.

So I did it this way


when ST_MCP25625_TO_RAM_3 =>
    if (idx2 < 4) then
        tmp_mailbox(idx2) <= slave_data_out1;
        idx2 := idx2 + 1;
        RamState <= ST_UPDATE_RAM_ADDR;
  else
      mailbox_id := tmp_mailbox(3) & tmp_mailbox(2) & tmp_mailbox(1) & tmp_mailbox(0);
      RamState <= ST_MCP25625_TO_RAM_4;                                                        
end if;  
 
when ST_UPDATE_RAM_ADDR =>
    if (to_integer(unsigned(ram_addr_a)) < RAM_SIZE) then
       ram_addr_a <= ram_addr_a + 1;      
   end if;
  --this way the same problem
  --ram_addr_a <= std_logic_vector(to_unsigned(temp_mailbox_addr+idx2, 10));          
   RamState <= ST_MCP25625_TO_RAM_3;

And now I read

tmp_mailbox(0) = 5

tmp_mailbox(1) = 5

tmp_mailbox(2) = 6

tmp_mailbox(3) = 7

Where is my problem?

Altera_Forum · ‎04-30-2017

Have you got a testbench?

Altera_Forum · ‎05-01-2017

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Have you got a testbench?

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It's hard to simulate but I'll try.

Altera_Forum · ‎05-01-2017

Using a testbench is by far the easiest way to debug these things. With just a couple of code snippets, the is no way we can really see what's going on.