Primitive: 64-Deep by 4-bit Wide Multi Port Random Access Memory (Select RAM)
Introduction
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If the DIA, DIB, DIC, and DID inputs are all tied to the same data inputs, the RAM can become a 1 read/write port, 3 independent read port 64x1 quad port memory.
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If DID is grounded, DOD is not used.
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If ADDRA, ADDRB, and ADDRC are tied to the same address, the RAM becomes a 64x3 simple dual port RAM.
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If ADDRD is tied to ADDRA, ADDRB, and ADDRC, the RAM is a 64x4 single port RAM.
Port Descriptions
Port | Direction | Width | Function |
---|---|---|---|
DOA | Output | 1 | Read port data outputs addressed by ADDRA. |
DOB | Output | 1 | Read port data outputs addressed by ADDRB. |
DOC | Output | 1 | Read port data outputs addressed by ADDRC. |
DOD | Output | 1 | Read/Write port data outputs addressed by ADDRD. |
DIA | Input | 1 | Write data inputs addressed by ADDRD (read output is addressed by ADDRA). |
DIB | Input | 1 | Write data inputs addressed by ADDRD (read output is addressed by ADDRB). |
DIC | Input | 1 | Write data inputs addressed by ADDRD (read output is addressed by ADDRC). |
DID | Input | 1 | Write data inputs addressed by ADDRD. |
ADDRA | Input | 6 | Read address bus A. |
ADDRB | Input | 6 | Read address bus B. |
ADDRC | Input | 6 | Read address bus C. |
ADDRD | Input | 6 | 4-bit data write port, 1-bit data read port address bus D. |
WE | Input | 1 | Write Enable. |
WCLK | Input | 1 | Write clock (reads are asynchronous). |
Design Entry Method
Instantiation | Yes |
Inference | Recommended |
IP Catalog | No |
Macro support | No |
This element can be inferred by some synthesis tools by describing a RAM with a synchronous write and asynchronous read capability. Consult your synthesis tool documentation for details on RAM inference capabilities and coding examples. Xilinx suggests that you instantiate this component if you have a need to implicitly specify the RAM function, or if you need to manually place or relationally place the component. If a synchronous read capability is desired, the outputs can be connected to an FDRE (FDCE if asynchronous reset is needed) to improve the output timing of the function. However, this is not necessary for the proper operation of the RAM. If you want to have the data clocked on the negative edge of a clock, an inverter can be described on the clock input to this component. This inverter will be absorbed into the block giving the ability to write to the RAM on falling clock edges.
If instantiated, the following connections should be made to this component:
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Connect the WCLK input to the desired clock source, the DIA, DIB, DIC
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Connect the DIA, DIB, DIC, and DID inputs to the data source to be stored
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Connect the DOA, DOB, DOC, and DOD outputs to an FDCE D input or other appropriate data destination, or leave unconnected if not used
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Connect the WE clock enable pin to the proper write enable source in the design
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Connect the ADDRD bus to the source for the read/write addressing
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Connect the ADDRA, ADDRB, and ADDRC buses to the appropriate read address connections
The optional INIT_A, INIT_B, INIT_C and INIT_D attributes let you specify the initial memory contents of each port using a 64-bit hexadecimal value. The INIT value correlates to the RAM addressing by the following equation: ADDRy[z] = INIT_y[z]. For instance, if the RAM ADDRC port is addressed to 00001, then the INIT_C[1] values would be the initial values shown on the DOC port before the first write occurs at that address. If left unspecified, the initial contents will default to all zeros.
Available Attributes
Attribute | Type | Allowed Values | Default | Description |
---|---|---|---|---|
INIT_A | HEX | Any 64-bit value | All zero | Specifies the initial contents of the RAM on port A. |
INIT_B | HEX | Any 64-bit value | All zero | Specifies the initial contents of the RAM on port B. |
INIT_C | HEX | Any 64-bit value | All zero | Specifies the initial contents of the RAM on port C. |
INIT_D | HEX | Any 64-bit value | All zero | Specifies the initial contents of the RAM on port D. |
VHDL Instantiation Template
Library UNISIM;
use UNISIM.vcomponents.all;
-- RAM64M: 64-deep by 4-wide Multi Port LUT RAM (Mapped to four SliceM LUT6s)
-- 7 Series
-- Xilinx HDL Language Template, version 2022.2
RAM64M_inst : RAM64M
generic map (
INIT_A => X"0000000000000000", -- Initial contents of A port
INIT_B => X"0000000000000000", -- Initial contents of B port
INIT_C => X"0000000000000000", -- Initial contents of C port
INIT_D => X"0000000000000000") -- Initial contents of D port
port map (
DOA => DOA, -- Read port A 1-bit output
DOB => DOB, -- Read port B 1-bit output
DOC => DOC, -- Read port C 1-bit output
DOD => DOD, -- Read/Write port D 1-bit output
ADDRA => ADDRA, -- Read port A 6-bit address input
ADDRB => ADDRB, -- Read port B 6-bit address input
ADDRC => ADDRC, -- Read port C 6-bit address input
ADDRD => ADDRD, -- Read/Write port D 6-bit address input
DIA => DIA, -- RAM 1-bit data write input addressed by ADDRD,
-- read addressed by ADDRA
DIB => DIB, -- RAM 1-bit data write input addressed by ADDRD,
-- read addressed by ADDRB
DIC => DIC, -- RAM 1-bit data write input addressed by ADDRD,
-- read addressed by ADDRC
DID => DID, -- RAM 1-bit data write input addressed by ADDRD,
-- read addressed by ADDRD
WCLK => WCLK, -- Write clock input
WE => WE -- Write enable input
);
-- End of RAM64M_inst instantiation
Verilog Instantiation Template
// RAM64M: 64-deep by 4-wide Multi Port LUT RAM (Mapped to four SliceM LUT6s)
// 7 Series
// Xilinx HDL Language Template, version 2022.2
RAM64M #(
.INIT_A(64'h0000000000000000), // Initial contents of A Port
.INIT_B(64'h0000000000000000), // Initial contents of B Port
.INIT_C(64'h0000000000000000), // Initial contents of C Port
.INIT_D(64'h0000000000000000) // Initial contents of D Port
) RAM64M_inst (
.DOA(DOA), // Read port A 1-bit output
.DOB(DOB), // Read port B 1-bit output
.DOC(DOC), // Read port C 1-bit output
.DOD(DOD), // Read/write port D 1-bit output
.DIA(DIA), // RAM 1-bit data write input addressed by ADDRD,
// read addressed by ADDRA
.DIB(DIB), // RAM 1-bit data write input addressed by ADDRD,
// read addressed by ADDRB
.DIC(DIC), // RAM 1-bit data write input addressed by ADDRD,
// read addressed by ADDRC
.DID(DID), // RAM 1-bit data write input addressed by ADDRD,
// read addressed by ADDRD
.ADDRA(ADDRA), // Read port A 6-bit address input
.ADDRB(ADDRB), // Read port B 6-bit address input
.ADDRC(ADDRC), // Read port C 6-bit address input
.ADDRD(ADDRD), // Read/write port D 6-bit address input
.WE(WE), // Write enable input
.WCLK(WCLK) // Write clock input
);
// End of RAM64M_inst instantiation
Related Information
- See the 7 Series FPGAs Configurable Logic Block User Guide (UG474).