FIFO36E2 - 2024.1 English

UltraScale Architecture Libraries Guide (UG974)

Document ID
UG974
Release Date
2024-05-30
Version
2024.1 English

Primitive: 36Kb FIFO (First-In-First-Out) Block RAM Memory

  • PRIMITIVE_GROUP: BLOCKRAM
  • PRIMITIVE_SUBGROUP: FIFO
  • Families: UltraScale, UltraScale+

Introduction

The FIFO36E2 uses dedicated control logic and the 36 Kb Block RAM to deliver a configurable First-In-First-Out (FIFO) capability. This primitive can be used in a 4-bit wide by 8K deep, 9-bit wide by 4K deep, 18-bit wide by 2K deep, 36-bit by 1K deep or a 72-bit wide by 512 deep configuration. The primitive can be configured in synchronous or dual-clock (asynchronous) mode, with all associated FIFO flags and status signals. This FIFO also features a cascade capability which lets you chain multiple FIFO36E2 components to form deeper FIFO configurations if desired.

When using the dual-clock mode with independent clocks, depending on the offset between read and write clock edges, the Empty, Almost Empty, Full, and Almost Full flags can deassert one cycle later. Due to the asynchronous nature of the clocks, the simulation model only reflects the deassertion latency cycles listed in the User Guide.

Port Descriptions

Port Direction Width Function
Cascade Signals: Signals used when cascading more than one FIFO.
CASDIN<63:0> Input 64 Data input bus from previous CASDOUT bus when cascading FIFOs serially or in parallel to extend depth. Only used when CASCADE_ORDER="MIDDLE", "LAST", or "PARALLEL".
CASDINP<7:0> Input 8 Parity data input bus from previous CASDOUTP bus when cascading FIFOs serially or in parallel to extend depth. Only used when CASCADE_ORDER="MIDDLE", "LAST", or "PARALLEL".
CASDOMUX Input 1 D input to flop that drives the select line to the cascade mux on the block RAM outputs. Only used when CASCADE_ORDER="PARALLEL".
CASDOMUXEN Input 1 EN input to flop that drives the select line to the cascade mux on the block RAM outputs. Only used when CASCADE_ORDER="PARALLEL".
CASDOUT<63:0> Output 64 Data output bus to next CASDIN bus when cascading FIFOs serially or in parallel to extend depth. Only used when CASCADE_ORDER="FIRST", "MIDDLE", or "PARALLEL".
CASDOUTP<7:0> Output 8 Parity data output bus to next CASDINP bus when cascading FIFOs serially or in parallel to extend depth. Only used when CASCADE_ORDER="FIRST", "MIDDLE", or "PARALLEL".
CASNXTEMPTY Output 1 EMPTY input from previous FIFO, used for cascading FIFOs serially to extend depth. Connects to the CASNXTEMPTY of the previous FIFO. Only used when CASCADE_ORDER="MIDDLE" or "LAST".
CASNXTRDEN Input 1 RDEN input from next FIFO, used for cascading FIFOs serially to extend depth. Connects to CASPRVRDEN of the next FIFO. Only used when CASCADE_ORDER="FIRST" or "MIDDLE".
CASOREGIMUX Input 1 D input to flop that drives the select line to the cascade mux before the output registers. Only used when CASCADE_ORDER="PARALLEL" and REGISTER_MODE="DO_PIPELINED".
CASOREGIMUXEN Input 1 EN input to flop that drives the select line to the cascade mux before the output registers. Only used when CASCADE_ORDER="PARALLEL" and REGISTER_MODE="DO_PIPELINED".
CASPRVEMPTY Input 1 EMPTY input from previous FIFO, used for cascading FIFOs serially to extend depth. Connects to the CASNXTEMPTY of the previous FIFO. Only used when CASCADE_ORDER="MIDDLE" or "LAST".
CASPRVRDEN Output 1 Control output driving the RDEN input of the previous (PRV) FIFO, used for cascading FIFOs serially to extend depth. Connects to CASNXTRDEN of the previous FIFO. Only used when CASCADE_ORDER="MIDDLE" or "LAST".
ECC Signals: Error Correction Circuitry ports.
DBITERR Output 1 Status output from ECC function to indicate a double bit error was detected during a read operation. EN_ECC_READ needs to be TRUE to use this functionality. Synchronous to RDCLK.
ECCPARITY<7:0> Output 8 8-bit data generated by the ECC encoder used by the ECC decoder for memory error detection and correction. Applicable when EN_ECC_WRITE=1. Synchronous to WRCLK.
INJECTDBITERR Input 1 Applicable when EN_ECC_WRITE=1. Causes a double-bit error to be inserted on bits 30 and 62 of DI during a write operation. Synchronous to WRCLK.
INJECTSBITERR Input 1 Applicable when EN_ECC_WRITE=1. Causes a single-bit error to be inserted on bit 30 of DI during a write operation.
SBITERR Output 1 ECC output indicating that a single-bit error was detected during the read operation. Synchronous to RDCLK.
Read Control Signals: Read clock, enable and reset input signals.
RDCLK Input 1 Read clock.
RDEN Input 1 Active-High read enable.
REGCE Input 1 Active-High enable for output register stage.
RSTREG Input 1 Active-High enable for output register reset.
SLEEP Input 1 Dynamic shut down power saving. If SLEEP is High, the block is in power saving mode. If SLEEP_ASYNC=FALSE, synchronous to RDCLK, otherwise, asynchronous input.
Read Data: Read output data.
DOUT<63:0> Output 64 FIFO data output bus. Synchronous to RDCLK.
DOUTP<7:0> Output 8 FIFO parity output bus. Synchronous to RDCLK.
Status: Flags and other FIFO status outputs.
EMPTY Output 1 Active-High flag to indicate when the FIFO is empty. Synchronous to RDCLK.
FULL Output 1 Active-High flag to indicate when the FIFO is full. Synchronous to WRCLK.
PROGEMPTY Output 1 Programmable flag to indicate the FIFO is almost empty (contains less than or equal to the number of words specified by the PROG_EMPTY_THRESH). Synchronous to RDCLK.
PROGFULL Output 1 Programmable flag to indicate the FIFO is almost full (contains greater than or equal to the number of words specified by the PROG_FULL_THRESH) Synchronous to WRCLK.
RDCOUNT<13:0> Output 14 Output of the internal FIFO read pointer, or a count of the number of words in the FIFO. Synchronous to RDCLK. Output value controlled by RDCOUNT_TYPE.
RDERR Output 1 Indicates that a read operation failed due to FIFO being EMPTY, or FIFO being in a reset condition. Synchronous to RDCLK.
RDRSTBUSY Output 1 Active-High indicator that the FIFO is currently in a reset state. Synchronous to RDCLK.
WRCOUNT<13:0> Output 14 Output of the internal FIFO write pointer, or a count of the number of words in the FIFO. Synchronous to WRCLK. Output value controlled by WRCOUNT_TYPE.
WRERR Output 1 Indicates that a write operation failed due to FIFO being FULL, or FIFO being in a reset condition. Synchronous to WRCLK.
WRRSTBUSY Output 1 Active-High indicator that the FIFO is currently in a reset state. Synchronous to WRCLK.
Write Control Signals: Write clock and enable input signals.
RST Input 1 Active-High synchronous reset. Synchronous to WRCLK.
WRCLK Input 1 Write clock.
WREN Input 1 Active-High write enable.
Write Data: Write input data.
DIN<63:0> Input 64 FIFO data input bus. Synchronous to WRCLK.
DINP<7:0> Input 8 FIFO parity input bus. Synchronous to WRCLK.

Design Entry Method

Instantiation Yes
Inference No
IP and IP Integrator Catalog Yes

Available Attributes

Attribute Type Allowed Values Default Description
CASCADE_ORDER STRING "NONE", "FIRST", "LAST", "MIDDLE", "PARALLEL" "NONE" Specifies use, configuration and position of the cascade feature to bind more than one FIFO36E2 together to form deeper FIFO depths.
CLOCK_DOMAINS STRING "INDEPENDENT", "COMMON" "INDEPENDENT" Specifies whether to use a Common (synchronous operation) or Independent (asynchronous or different) clocks.
EN_ECC_PIPE STRING "FALSE", "TRUE" "FALSE" Enable ECC pipeline output register stage.
EN_ECC_READ STRING "FALSE", "TRUE" "FALSE" Enable the ECC read decoder circuitry. Only valid when READ_WIDTH is set to 72.
EN_ECC_WRITE STRING "FALSE", "TRUE" "FALSE" Enable the ECC write encoder circuitry. Only valid when WRITE_WIDTH is set to 72.
FIRST_WORD_FALL_THROUGH STRING "FALSE", "TRUE" "FALSE" If TRUE, the first write to the FIFO will appear on DO without a first RDEN assertion.
INIT HEX Any 72-bit HEX value All zeroes Specifies the initial value on the DO output after configuration.
PROG_EMPTY_THRESH DECIMAL 1 to 8191 256 Specifies the different between the write pointer (WRCOUNT) and read pointer (RDCOUNT). to trigger the PROGEMPTY output.
PROG_FULL_THRESH DECIMAL 1 to 8191 256 Specifies the different between the write pointer (WRCOUNT) and read pointer (RDCOUNT). to trigger the PROGFULL output.
RDCOUNT_TYPE STRING "RAW_PNTR", "EXTENDED_DATACOUNT", "SIMPLE_DATACOUNT", "SYNC_PNTR" "RAW_PNTR" Specifies type and format for the RDCOUNT data.
READ_WIDTH DECIMAL 4, 9, 18, 36, 72 4 Specifies the data width for the read-side of the FIFO.
REGISTER_MODE STRING "UNREGISTERED", "DO_PIPELINED", "REGISTERED" "UNREGISTERED" Specifies output register mode.
RSTREG_PRIORITY STRING "RSTREG", "REGCE" "RSTREG" Specifies whether reset or enable has priority.
SLEEP_ASYNC STRING "FALSE", "TRUE" "FALSE" Specifies asynchronous or synchronous operation of the BRAM sleep mode.
SRVAL HEX Any 72-bit HEX value All zeroes Specifies per-bit the polarity of the FIFO output after RST/RSTREG is asserted
WRCOUNT_TYPE STRING "RAW_PNTR", "EXTENDED_DATACOUNT", "SIMPLE_DATACOUNT", "SYNC_PNTR" "RAW_PNTR" Specifies type and format for the WRCOUNT data.
WRITE_WIDTH DECIMAL 4, 9, 18, 36, 72 4 Specifies the data width for the write-side of the FIFO.
Programmable Inversion Attributes: Specifies whether or not to use the optional inversions on specific pins of this component to change the active polarity of the pin function. When set to 1 on a clock pin (WRCLK or RDCLK), this components clocks on the negative edge. When set to 1 on other pins, it changes the function to behave active-Low rather than active-High. For pins that are buses, the bit-width of this attribute should match that of the bit-width of the associated pins and a binary value indicates which inverters to use and which to bypass. If an external inverter is specified on one of these associated pins, the Vivado Design Suite will automatically set this attribute during the opt_design stage so that additional logic is not necessary for changing the input polarity.
IS_RDCLK_INVERTED BINARY 1'b0 to 1'b1 1'b0 Specifies whether or not to use the optional inversion on the RDCLK pin.
IS_RDEN_INVERTED BINARY 1'b0 to 1'b1 1'b0 Specifies whether or not to use the optional inversion on the RDEN pin.
IS_RST_INVERTED BINARY 1'b0 to 1'b1 1'b0 Specifies whether or not to use the optional inversion on the RST pin.
IS_RSTREG_INVERTED BINARY 1'b0 to 1'b1 1'b0 Specifies whether or not to use the optional inversion on the RSTREG pin.
IS_WRCLK_INVERTED BINARY 1'b0 to 1'b1 1'b0 Specifies whether or not to use the optional inversion on the WRCLK pin.
IS_WREN_INVERTED BINARY 1'b0 to 1'b1 1'b0 Specifies whether or not to use the optional inversion on the WREN pin.

VHDL Instantiation Template

Unless they already exist, copy the following two statements and paste them before the entity declaration.
Library UNISIM;
use UNISIM.vcomponents.all;

-- FIFO36E2: 36Kb FIFO (First-In-First-Out) Block RAM Memory
--           UltraScale
-- Xilinx HDL Language Template, version 2024.1

FIFO36E2_inst : FIFO36E2
generic map (
   CASCADE_ORDER => "NONE",            -- FIRST, LAST, MIDDLE, NONE, PARALLEL
   CLOCK_DOMAINS => "INDEPENDENT",     -- COMMON, INDEPENDENT
   EN_ECC_PIPE => "FALSE",             -- ECC pipeline register, (FALSE, TRUE)
   EN_ECC_READ => "FALSE",             -- Enable ECC decoder, (FALSE, TRUE)
   EN_ECC_WRITE => "FALSE",            -- Enable ECC encoder, (FALSE, TRUE)
   FIRST_WORD_FALL_THROUGH => "FALSE", -- FALSE, TRUE
   INIT => X"000000000000000000",      -- Initial values on output port
   PROG_EMPTY_THRESH => 256,           -- Programmable Empty Threshold
   PROG_FULL_THRESH => 256,            -- Programmable Full Threshold
   -- Programmable Inversion Attributes: Specifies the use of the built-in programmable inversion
   IS_RDCLK_INVERTED => '0',           -- Optional inversion for RDCLK
   IS_RDEN_INVERTED => '0',            -- Optional inversion for RDEN
   IS_RSTREG_INVERTED => '0',          -- Optional inversion for RSTREG
   IS_RST_INVERTED => '0',             -- Optional inversion for RST
   IS_WRCLK_INVERTED => '0',           -- Optional inversion for WRCLK
   IS_WREN_INVERTED => '0',            -- Optional inversion for WREN
   RDCOUNT_TYPE => "RAW_PNTR",         -- EXTENDED_DATACOUNT, RAW_PNTR, SIMPLE_DATACOUNT, SYNC_PNTR
   READ_WIDTH => 4,                    -- 18-9
   REGISTER_MODE => "UNREGISTERED",    -- DO_PIPELINED, REGISTERED, UNREGISTERED
   RSTREG_PRIORITY => "RSTREG",        -- REGCE, RSTREG
   SLEEP_ASYNC => "FALSE",             -- FALSE, TRUE
   SRVAL => X"000000000000000000",     -- SET/reset value of the FIFO outputs
   WRCOUNT_TYPE => "RAW_PNTR",         -- EXTENDED_DATACOUNT, RAW_PNTR, SIMPLE_DATACOUNT, SYNC_PNTR
   WRITE_WIDTH => 4                    -- 18-9
)
port map (
   -- Cascade Signals outputs: Multi-FIFO cascade signals
   CASDOUT => CASDOUT,             -- 64-bit output: Data cascade output bus
   CASDOUTP => CASDOUTP,           -- 8-bit output: Parity data cascade output bus
   CASNXTEMPTY => CASNXTEMPTY,     -- 1-bit output: Cascade next empty
   CASPRVRDEN => CASPRVRDEN,       -- 1-bit output: Cascade previous read enable
   -- ECC Signals outputs: Error Correction Circuitry ports
   DBITERR => DBITERR,             -- 1-bit output: Double bit error status
   ECCPARITY => ECCPARITY,         -- 8-bit output: Generated error correction parity
   SBITERR => SBITERR,             -- 1-bit output: Single bit error status
   -- Read Data outputs: Read output data
   DOUT => DOUT,                   -- 64-bit output: FIFO data output bus
   DOUTP => DOUTP,                 -- 8-bit output: FIFO parity output bus.
   -- Status outputs: Flags and other FIFO status outputs
   EMPTY => EMPTY,                 -- 1-bit output: Empty
   FULL => FULL,                   -- 1-bit output: Full
   PROGEMPTY => PROGEMPTY,         -- 1-bit output: Programmable empty
   PROGFULL => PROGFULL,           -- 1-bit output: Programmable full
   RDCOUNT => RDCOUNT,             -- 14-bit output: Read count
   RDERR => RDERR,                 -- 1-bit output: Read error
   RDRSTBUSY => RDRSTBUSY,         -- 1-bit output: Reset busy (sync to RDCLK)
   WRCOUNT => WRCOUNT,             -- 14-bit output: Write count
   WRERR => WRERR,                 -- 1-bit output: Write Error
   WRRSTBUSY => WRRSTBUSY,         -- 1-bit output: Reset busy (sync to WRCLK)
   -- Cascade Signals inputs: Multi-FIFO cascade signals
   CASDIN => CASDIN,               -- 64-bit input: Data cascade input bus
   CASDINP => CASDINP,             -- 8-bit input: Parity data cascade input bus
   CASDOMUX => CASDOMUX,           -- 1-bit input: Cascade MUX select input
   CASDOMUXEN => CASDOMUXEN,       -- 1-bit input: Enable for cascade MUX select
   CASNXTRDEN => CASNXTRDEN,       -- 1-bit input: Cascade next read enable
   CASOREGIMUX => CASOREGIMUX,     -- 1-bit input: Cascade output MUX select
   CASOREGIMUXEN => CASOREGIMUXEN, -- 1-bit input: Cascade output MUX select enable
   CASPRVEMPTY => CASPRVEMPTY,     -- 1-bit input: Cascade previous empty
   -- ECC Signals inputs: Error Correction Circuitry ports
   INJECTDBITERR => INJECTDBITERR, -- 1-bit input: Inject a double-bit error
   INJECTSBITERR => INJECTSBITERR, -- 1-bit input: Inject a single bit error
   -- Read Control Signals inputs: Read clock, enable and reset input signals
   RDCLK => RDCLK,                 -- 1-bit input: Read clock
   RDEN => RDEN,                   -- 1-bit input: Read enable
   REGCE => REGCE,                 -- 1-bit input: Output register clock enable
   RSTREG => RSTREG,               -- 1-bit input: Output register reset
   SLEEP => SLEEP,                 -- 1-bit input: Sleep Mode
   -- Write Control Signals inputs: Write clock and enable input signals
   RST => RST,                     -- 1-bit input: Reset
   WRCLK => WRCLK,                 -- 1-bit input: Write clock
   WREN => WREN,                   -- 1-bit input: Write enable
   -- Write Data inputs: Write input data
   DIN => DIN,                     -- 64-bit input: FIFO data input bus
   DINP => DINP                    -- 8-bit input: FIFO parity input bus
);

-- End of FIFO36E2_inst instantiation

Verilog Instantiation Template


// FIFO36E2: 36Kb FIFO (First-In-First-Out) Block RAM Memory
//           UltraScale
// Xilinx HDL Language Template, version 2024.1

FIFO36E2 #(
   .CASCADE_ORDER("NONE"),            // FIRST, LAST, MIDDLE, NONE, PARALLEL
   .CLOCK_DOMAINS("INDEPENDENT"),     // COMMON, INDEPENDENT
   .EN_ECC_PIPE("FALSE"),             // ECC pipeline register, (FALSE, TRUE)
   .EN_ECC_READ("FALSE"),             // Enable ECC decoder, (FALSE, TRUE)
   .EN_ECC_WRITE("FALSE"),            // Enable ECC encoder, (FALSE, TRUE)
   .FIRST_WORD_FALL_THROUGH("FALSE"), // FALSE, TRUE
   .INIT(72'h000000000000000000),     // Initial values on output port
   .PROG_EMPTY_THRESH(256),           // Programmable Empty Threshold
   .PROG_FULL_THRESH(256),            // Programmable Full Threshold
   // Programmable Inversion Attributes: Specifies the use of the built-in programmable inversion
   .IS_RDCLK_INVERTED(1'b0),          // Optional inversion for RDCLK
   .IS_RDEN_INVERTED(1'b0),           // Optional inversion for RDEN
   .IS_RSTREG_INVERTED(1'b0),         // Optional inversion for RSTREG
   .IS_RST_INVERTED(1'b0),            // Optional inversion for RST
   .IS_WRCLK_INVERTED(1'b0),          // Optional inversion for WRCLK
   .IS_WREN_INVERTED(1'b0),           // Optional inversion for WREN
   .RDCOUNT_TYPE("RAW_PNTR"),         // EXTENDED_DATACOUNT, RAW_PNTR, SIMPLE_DATACOUNT, SYNC_PNTR
   .READ_WIDTH(4),                    // 18-9
   .REGISTER_MODE("UNREGISTERED"),    // DO_PIPELINED, REGISTERED, UNREGISTERED
   .RSTREG_PRIORITY("RSTREG"),        // REGCE, RSTREG
   .SLEEP_ASYNC("FALSE"),             // FALSE, TRUE
   .SRVAL(72'h000000000000000000),    // SET/reset value of the FIFO outputs
   .WRCOUNT_TYPE("RAW_PNTR"),         // EXTENDED_DATACOUNT, RAW_PNTR, SIMPLE_DATACOUNT, SYNC_PNTR
   .WRITE_WIDTH(4)                    // 18-9
)
FIFO36E2_inst (
   // Cascade Signals outputs: Multi-FIFO cascade signals
   .CASDOUT(CASDOUT),             // 64-bit output: Data cascade output bus
   .CASDOUTP(CASDOUTP),           // 8-bit output: Parity data cascade output bus
   .CASNXTEMPTY(CASNXTEMPTY),     // 1-bit output: Cascade next empty
   .CASPRVRDEN(CASPRVRDEN),       // 1-bit output: Cascade previous read enable
   // ECC Signals outputs: Error Correction Circuitry ports
   .DBITERR(DBITERR),             // 1-bit output: Double bit error status
   .ECCPARITY(ECCPARITY),         // 8-bit output: Generated error correction parity
   .SBITERR(SBITERR),             // 1-bit output: Single bit error status
   // Read Data outputs: Read output data
   .DOUT(DOUT),                   // 64-bit output: FIFO data output bus
   .DOUTP(DOUTP),                 // 8-bit output: FIFO parity output bus.
   // Status outputs: Flags and other FIFO status outputs
   .EMPTY(EMPTY),                 // 1-bit output: Empty
   .FULL(FULL),                   // 1-bit output: Full
   .PROGEMPTY(PROGEMPTY),         // 1-bit output: Programmable empty
   .PROGFULL(PROGFULL),           // 1-bit output: Programmable full
   .RDCOUNT(RDCOUNT),             // 14-bit output: Read count
   .RDERR(RDERR),                 // 1-bit output: Read error
   .RDRSTBUSY(RDRSTBUSY),         // 1-bit output: Reset busy (sync to RDCLK)
   .WRCOUNT(WRCOUNT),             // 14-bit output: Write count
   .WRERR(WRERR),                 // 1-bit output: Write Error
   .WRRSTBUSY(WRRSTBUSY),         // 1-bit output: Reset busy (sync to WRCLK)
   // Cascade Signals inputs: Multi-FIFO cascade signals
   .CASDIN(CASDIN),               // 64-bit input: Data cascade input bus
   .CASDINP(CASDINP),             // 8-bit input: Parity data cascade input bus
   .CASDOMUX(CASDOMUX),           // 1-bit input: Cascade MUX select input
   .CASDOMUXEN(CASDOMUXEN),       // 1-bit input: Enable for cascade MUX select
   .CASNXTRDEN(CASNXTRDEN),       // 1-bit input: Cascade next read enable
   .CASOREGIMUX(CASOREGIMUX),     // 1-bit input: Cascade output MUX select
   .CASOREGIMUXEN(CASOREGIMUXEN), // 1-bit input: Cascade output MUX select enable
   .CASPRVEMPTY(CASPRVEMPTY),     // 1-bit input: Cascade previous empty
   // ECC Signals inputs: Error Correction Circuitry ports
   .INJECTDBITERR(INJECTDBITERR), // 1-bit input: Inject a double-bit error
   .INJECTSBITERR(INJECTSBITERR), // 1-bit input: Inject a single bit error
   // Read Control Signals inputs: Read clock, enable and reset input signals
   .RDCLK(RDCLK),                 // 1-bit input: Read clock
   .RDEN(RDEN),                   // 1-bit input: Read enable
   .REGCE(REGCE),                 // 1-bit input: Output register clock enable
   .RSTREG(RSTREG),               // 1-bit input: Output register reset
   .SLEEP(SLEEP),                 // 1-bit input: Sleep Mode
   // Write Control Signals inputs: Write clock and enable input signals
   .RST(RST),                     // 1-bit input: Reset
   .WRCLK(WRCLK),                 // 1-bit input: Write clock
   .WREN(WREN),                   // 1-bit input: Write enable
   // Write Data inputs: Write input data
   .DIN(DIN),                     // 64-bit input: FIFO data input bus
   .DINP(DINP)                    // 8-bit input: FIFO parity input bus
);

// End of FIFO36E2_inst instantiation

Related Information

  • UltraScale Architecture Memory Resources User Guide (UG573)