Where does Vivado reference primitives when building the implemented design?

Question

I'm trying to figure out exactly what file vivado uses to create the attributes of a primitive block. I'm trying to do an experiment with removing some of the properties but no matter what file I edit they always reappear after implementation. Specifically, I'm using an Artix-7 and I'm trying to modify the attributes of the block ram.

Answer 1

Vivado has two different methods for instantiating primitives:

• Direct instantiation: You explicitly write a macro and you connect all the signals accordingly. In this case the macro is parametrizable and the properties you write during instantiation are 1:1 matching with the primitive instantiation in the netlist.

• Inferring: you write some templated code which then the synthesizer recognize and transform in the equivalent primitive. Controlling primitives here is more complicated and depends on a mix of instantiation style and RTL attributes.

You can find more information in the 7series library guide.

For your question, let's take a look at the BRAM_TDP_MACRO. Here's the direct instantiation template:

BRAM_TDP_MACRO_inst : BRAM_TDP_MACRO
generic map (
BRAM_SIZE => "18Kb", -- Target BRAM, "18Kb" or "36Kb"
DEVICE => "7SERIES", -- Target Device: "VIRTEX5", "VIRTEX6", "7SERIES", "SPARTAN6"
DOA_REG => 0, -- Optional port A output register (0 or 1)
DOB_REG => 0, -- Optional port B output register (0 or 1)
INIT_A => X"000000000", -- Initial values on A output port
INIT_B => X"000000000", -- Initial values on B output port
INIT_FILE => "NONE",
READ_WIDTH_A => 0, -- Valid values are 1-36 (19-36 only valid when BRAM_SIZE="36Kb")
READ_WIDTH_B => 0, -- Valid values are 1-36 (19-36 only valid when BRAM_SIZE="36Kb")
SIM_COLLISION_CHECK => "ALL", -- Collision check enable "ALL", "WARNING_ONLY",
-- "GENERATE_X_ONLY" or "NONE"
SRVAL_A => X"000000000", -- Set/Reset value for A port output
SRVAL_B => X"000000000", -- Set/Reset value for B port output
WRITE_MODE_A => "WRITE_FIRST", -- "WRITE_FIRST", "READ_FIRST" or "NO_CHANGE"
WRITE_MODE_B => "WRITE_FIRST", -- "WRITE_FIRST", "READ_FIRST" or "NO_CHANGE"
WRITE_WIDTH_A => 0, -- Valid values are 1-36 (19-36 only valid when BRAM_SIZE="36Kb")
WRITE_WIDTH_B => 0, -- Valid values are 1-36 (19-36 only valid when BRAM_SIZE="36Kb"),
port map (
DOA => DOA, -- Output port-A data, width defined by READ_WIDTH_A parameter
DOB => DOB, -- Output port-B data, width defined by READ_WIDTH_B parameter
ADDRA => ADDRA, -- Input port-A address, width defined by Port A depth
ADDRB => ADDRB, -- Input port-B address, width defined by Port B depth
CLKA => CLKA, -- 1-bit input port-A clock
CLKB => CLKB, -- 1-bit input port-B clock
DIA => DIA, -- Input port-A data, width defined by WRITE_WIDTH_A parameter
DIB => DIB, -- Input port-B data, width defined by WRITE_WIDTH_B parameter
ENA => ENA, -- 1-bit input port-A enable
ENB => ENB, -- 1-bit input port-B enable
REGCEA => REGCEA, -- 1-bit input port-A output register enable
REGCEB => REGCEB, -- 1-bit input port-B output register enable
RSTA => RSTA, -- 1-bit input port-A reset
RSTB => RSTB, -- 1-bit input port-B reset
WEA => WEA, -- Input port-A write enable, width defined by Port A depth
WEB => WEB -- Input port-B write enable, width defined by Port B depth
);

And here (page 132) instead a possible way to have it inferred.