Forum Discussion
Altera_Forum
Honored Contributor
Honored Contributorimplement 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
);11 Replies
Altera_ForumI think you must set the ram_block_type parameter to "MLAB"
- Altera_Forum
adding
in the generic map should force use of the smaller 640-bit sized MLAB memory blockslpm_hint => "RAM_BLOCK_TYPE=MLAB", - Altera_Forum
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--- 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
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:
Thx JulienParameter 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. - Altera_Forum
Indeed, I should have copied a bit more from my code:
will force usage of LE-registers to build the memory blockuse_eab => "OFF", - Altera_Forum
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
@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
up: so does use_eab => "OFF" works for altsyncrams?
- Altera_Forum--- 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?
