Primitive: 64-Deep by 4-bit Wide Multi Port Random Access Memory (Select RAM)
- PRIMITIVE_GROUP: CLB
- PRIMITIVE_SUBGROUP: LUTRAM
Introduction
-
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.
-
If DID is grounded, DOD is not used.
-
If ADDRA, ADDRB, and ADDRC are tied to the same address, the RAM becomes a 64x3 simple dual port RAM.
-
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 |
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 synchronous read capability is desired, the outputs can be connected to an FDRE/FDSE (FDCE/FDPE if asynchronous reset is needed) in order 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 during implementation and set as the IS_WCLK_INVERTED attribute giving the ability to write to the RAM on falling clock edges.
-
Connect the WCLK input to the desired clock source, the DIA, DIB, DIC
-
Connect the DIA, DIB, DIC, and DID inputs to the data source to be stored
-
Connect the DOA, DOB, DOC, and DOD outputs to an FDCE D input or other appropriate data destination, or leave unconnected if not used
-
Connect the WE clock enable pin to the proper write enable source in the design
-
Connect the ADDRD bus to the source for the read/write addressing
-
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 zeros | Specifies the initial contents of the RAM on port A. |
INIT_B | HEX | Any 64-bit value | All zeros | Specifies the initial contents of the RAM on port B. |
INIT_C | HEX | Any 64-bit value | All zeros | Specifies the initial contents of the RAM on port C. |
INIT_D | HEX | Any 64-bit value | All zeros | Specifies the initial contents of the RAM on port D. |
IS_WCLK_INVERTED | BINARY | 1'b0 to 1'b1 | 1'b0 | Specifies whether or not to use the optional inversion on the WCLK pin. |
VHDL Instantiation Template
Library UNISIM;
use UNISIM.vcomponents.all;
Verilog Instantiation Template
Related Information
- Versal Adaptive SoC Configurable Logic Block Architecture Manual (AM005)