Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Altera_Forum
Honored Contributor I
1,995 Views

implement ram with logic blocks

Hi all! 

 

I am designing an Avalon-MM interface with a page system: a page register is used as address of a memory and a data register is used to read/write the memory. 

 

The memory I instanciate is an altsyncram. 

 

For functional purpose I need a true dual port memory (1 port for Avalon-MM, 1 port for core processing). 

 

channel_dst_mac_addr_ram : altsyncram generic map ( lpm_type => "altsyncram", intended_device_family => "Stratix IV", power_up_uninitialized => "TRUE", operation_mode => "BIDIR_DUAL_PORT", outdata_reg_a => "CLOCK0", clock_enable_input_a => "BYPASS", address_reg_b => "CLOCK0", indata_reg_b => "CLOCK0", wrcontrol_wraddress_reg_b => "CLOCK0", outdata_reg_b => "CLOCK0", clock_enable_input_b => "BYPASS", numwords_a => NB_PAGES, numwords_b => NB_PAGES, widthad_a => pos_log2(NB_PAGES), widthad_b => pos_log2(NB_PAGES), width_a => 48, width_b => 48 ) port map ( clock0 => ast_clk, address_a => channel_dst_mac_addr_ram_address_a, wren_a => channel_dst_mac_addr_ram_wren_a, data_a => channel_dst_mac_addr_ram_data_a, q_a => channel_dst_mac_addr_ram_q_a, address_b => channel_dst_mac_addr_ram_address_b, wren_b => channel_dst_mac_addr_ram_wren_b, data_b => channel_dst_mac_addr_ram_data_b, q_b => channel_dst_mac_addr_ram_q_b ); 

 

 

My problem is that the number of pages I need (i.e. the memory depth) is usually quite low, like 2 or 3, but Quartus uses M9K to implement that memory. 

 

 

Is there an option to force the altsyncram to be implemented in logic blocks rather than in onchip RAMs, that I can turn on when NB_PGE is low? 

 

 

The system is for Stratix IV, I use Quartus 10.1. 

 

 

Thx
0 Kudos
11 Replies
Altera_Forum
Honored Contributor I
49 Views

I think you must set the ram_block_type parameter to "MLAB"

Altera_Forum
Honored Contributor I
49 Views

adding lpm_hint => "RAM_BLOCK_TYPE=MLAB", in the generic map should force use of the smaller 640-bit sized MLAB memory blocks

Altera_Forum
Honored Contributor I
49 Views

Quartus usually picks whetever is available. Is there any reason you specifically dont want an M9K? If there are plenty spare, whats the problem? 

 

Quartus should automatically pick MLABs if the M9Ks are getting a bit scarce.
Altera_Forum
Honored Contributor I
49 Views

 

--- Quote Start ---  

Quartus usually picks whetever is available. Is there any reason you specifically dont want an M9K? If there are plenty spare, whats the problem? 

--- Quote End ---  

 

There is never enough memory inside the chosen FPGA! :) 

 

--- Quote Start ---  

Quartus should automatically pick MLABs if the M9Ks are getting a bit scarce. 

--- Quote End ---  

 

 

This is not true! QII sometimes messes things up quite badly. I've seen it build a large memory with M4k and then using a M144k for a small fifo (Quartus II 9.1sp2 - Stratix II GX). I had to go through all my code and add the appropriate lpm_hint parameter to get the project fitted.
Altera_Forum
Honored Contributor I
49 Views

Agreed!! 

 

We are desperatly in need of memory and can't afford to waste M9K like this :( 

 

MLAB would be better than M9K, but my question was: is it even possible to force implementation with logic elements

 

I think there is an option like this for FIFOs: 

Parameter use_eab Type String Required No Description Specifies whether or not the FIFO megafunction is constructed using the RAM blocks. The values are ON or OFF. Setting this parameter value to OFF yields the FIFO megafunction implemented in logic elements regardless of the type of the TriMatrix memory block type assigned to the ram_block_type parameter.  

 

Thx 

 

Julien
Altera_Forum
Honored Contributor I
49 Views

Indeed, I should have copied a bit more from my code: 

use_eab => "OFF", 

will force usage of LE-registers to build the memory block
Altera_Forum
Honored Contributor I
49 Views

Since you said you only need 2 or 3 addresses, I'd build my own component using 2 or 3 48bit register arrays and a simple decoder.  

This would involve some coding, but it is likely to ensure a minimal resource implementation.
Altera_Forum
Honored Contributor I
49 Views

@Cris72: actually I said 'usually 2 or 3 addresses', but sometimes I can go up to several thousands. So I'll stick to the altsyncram. 

 

@josyb: so does use_eab => "OFF" works for altsyncrams?
Altera_Forum
Honored Contributor I
49 Views

up: so does use_eab => "OFF" works for altsyncrams?

Altera_Forum
Honored Contributor I
49 Views

 

--- Quote Start ---  

up: so does use_eab => "OFF" works for altsyncrams? 

--- Quote End ---  

 

 

I did use it once for a dcfifo, but I checked the help (QII 9.1sp2 and QII 11.1sp1) for altsyncram and there the parameter seems to be "IMPLEMENT_IN_LES" which you want to set to "ON". Why don't you try this?
Altera_Forum
Honored Contributor I
49 Views

Cool!! 

 

I have listed all the parameters of the altsyncram core in order to understand everything, and I could not figure out what that one meant. 

 

So now 1) I figured out what it is 2) it might solve my issue!! 

 

Thanks! 

 

I'll test that right now, and tell if it works 

 

Julien
Reply