Hi all! Many of Altera's 'Library Parametrizable Modules' (LPMs) have a 'lpm_hint' generic. This parameter is a string that is parsed, and can contain an arbitrary long list of parameter/value associations. Example: inst_1: lpm_mult generic map ( lpm_hint => "USE_EAB= ON, INPUT_A_IS_CONSTANT= YES"), Some of this parameter are explained in some documentations, but not all of them. Even for some LPMs no doc is available at all (e.g.: no mention to 'lpm_hint' in Altera's "Internal Memory (RAM and ROM) User Guide"... Where can I find info about that? Thx Julien

I think its an old thing that looks like it's dissapearing. IIRC, you used to have to use LPM_HINT on the DC/SCfifo to pass through memory paramters. But those paramters are part of the fifo params now. its also becoming less of an issue now that inference is so prevalent, and there is much less need to use the basic megafunctions. Plus the synthesisor is getting much better at working stuff out for you.

PS. I dont think the Altsyncram has an LPM hint parameter.

Actually, this question raised because I am trying to generate an altsyncram and there are parameters I dont understand in the component instanciated: --- Quote Start --- lpm_hint => "ENABLE_RUNTIME_MOD=NO", --- Quote End --- So I looked the entity into the file /opt/altera10.1/quartus/eda/simlib/altera_mf.vhd, and there are few parameters I don't get either: - sim_show_memory_data_in_port_b_layout - init_file_layout Do you know these? Thx

also, I see both a parameter "byte_size" and parameters "width_byteena_a" and "width_byteena_b". Shouldn't "width_byteena" be computed out of "width" and "byte_size", (or, on the contrary, "byte_size" be computed out of "width" and "width_byteena") ? Or should I just specify all of them, in coherence?

There seem to be more paramters in the Altera Help than in the User guide. For INIT_FILE_LAYOUT: --- Quote Start --- Specifies the layout port used with the initialization file. Values are "PORT_A", "PORT_B", and "UNUSED". If omitted, the default is "UNUSED". If the OPERATION_MODE is set to "DUAL_PORT" mode, the default value is "PORT_B". If the OPERATION_MODE is set to other modes, the default value is "PORT_A". --- Quote End --- There are not that many paramters that are required. Ususally I just omit anything I dont want to mess with specifically. Is there any reason you're using the mega-wizard and not using infered ram? Afaik, the only RAM you cannot infer is mixed-width true dual port dual clocked ram, or changing to write-before-read behaviour (this is annoying, because although a shared variable would allow you to do this, altera just infers read-before-write regardless. X does it properly). You can use attributes to specify some of the paramters like RAMSTYLE and init_files.

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Altera_Forum

Honored Contributor

14 years ago

lpm_hint

Hi all!

Many of Altera's 'Library Parametrizable Modules' (LPMs) have a 'lpm_hint' generic.

This parameter is a string that is parsed, and can contain an arbitrary long list of parameter/value associations.

Example:

inst_1: lpm_mult                                                              
generic map
(
    lpm_hint => "USE_EAB= ON, INPUT_A_IS_CONSTANT= YES"),

Some of this parameter are explained in some documentations, but not all of them.

Even for some LPMs no doc is available at all (e.g.: no mention to 'lpm_hint' in Altera's "Internal Memory (RAM and ROM) User Guide"...

Where can I find info about that?

Thx

Julien

12 Replies

Altera_Forum
Honored Contributor
14 years ago
Why not just do the code, and give them the results. They never need to know :)
Altera_Forum
Honored Contributor
14 years ago
Also remind them that Infered code is more portable (but you still have to be careful. Registers in Altera and Xilinx rams are placed slightly differently.

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lpm_hint

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