ece 448 – fpga and asic design with vhdl lecture 10 memories (ram/rom)

ECE 448 – FPGA and ASIC Design with VHDL

Lecture 10

Memories (RAM/ROM)

2

Outline

• Memory• Distributed RAM• Block RAM

• Instantiation versus Inference• VHDL Inference Code

• Distributed RAM• Block RAM• ROM

• VHDL Instantiation Code

3

Memory Types

4

Memory Types

Memory

RAM ROM

Single port Dual port

With asynchronous

read

With synchronous

read

Memory

Memory

5

FPGA Distributed

Memory

6

COUT

D Q

CK

S

REC

D Q

CK

REC

O

G4G3G2G1

Look-UpTable

Carry&

ControlLogic

O

YB

Y

F4F3F2F1

XB

X

Look-UpTable

F5IN

BYSR

S

Carry&

ControlLogic

CINCLKCE SLICE

CLB Slice

7

16-bit SR

16 x 1 RAM

4-input LUT

The Design Warrior’s Guide to FPGAsDevices, Tools, and Flows. ISBN 0750676043

Copyright © 2004 Mentor Graphics Corp. (www.mentor.com)

Xilinx Multipurpose LUT

8

RAM16X1S

O

DWE

WCLKA0A1A2A3

RAM32X1S

O

DWEWCLKA0A1A2A3A4

RAM16X2S

O1

D0

WEWCLKA0A1A2A3

D1

O0

=

=LUT

LUT or

LUT

RAM16X1D

SPO

D

WE

WCLK

A0

A1

A2

A3

DPRA0 DPO

DPRA1

DPRA2

DPRA3

or

Distributed RAM

• CLB LUT configurable as Distributed RAM• An LUT equals 16x1 RAM• Cascade LUTs to increase RAM size

• Synchronous write• Asynchronous read

• Can create a synchronous read by using extra flip-flops

• Naturally, distributed RAM read is asynchronous

• Two LUTs can make• 32 x 1 single-port RAM• 16 x 2 single-port RAM• 16 x 1 dual-port RAM

9

FPGA Block RAM

10

Block RAM

Spartan-3Dual-Port

Block RAM

Port A

Port B

Block RAM

• Most efficient memory implementation• Dedicated blocks of memory

• Ideal for most memory requirements• 4 to 104 memory blocks

• 18 kbits = 18,432 bits per block (16 k without parity bits)

• Use multiple blocks for larger memories• Builds both single and true dual-port RAMs• Synchronous write and read (different from distributed RAM)

11

RAM blocks

Multipliers

Logic blocks

RAM Blocks and Multipliers in Xilinx FPGAs

The Design Warrior’s Guide to FPGAsDevices, Tools, and Flows. ISBN 0750676043

Copyright © 2004 Mentor Graphics Corp. (www.mentor.com)

12

Spartan-3 Block RAM Amounts

13

Block RAM can have various configurations (port aspect ratios)

0

16,383

1

4,095

40

8,191

20

2047

8+10

1023

16+20

16k x 1

8k x 2 4k x 4

2k x (8+1)

1024 x (16+2)

14

Block RAM Port Aspect Ratios

15

Single-Port Block RAM

16

Dual-Port Block RAM

17

RAMB4_S16_S8

Port A Out18-Bit Width

Port B In2k-Bit Depth

Port A In1K-Bit Depth

Port B Out9-Bit Width

DOA[17:0]

DOB[8:0]

WEA

ENA

RSTA

ADDRA[9:0]

CLKA

DIA[17:0]

WEB

ENB

RSTB

ADDRB[10:0]

CLKB

DIB[8:0]

Dual-Port Bus Flexibility

• Each port can be configured with a different data bus width • Provides easy data width conversion without any additional logic

18

0, ADDR[12:0]

1, ADDR[12:0]

RAMB4_S1_S1

Port B Out1-Bit Width

DOA[0]

DOB[0]

WEA

ENA

RSTA

ADDRA[12:0]

CLKA

DIA[0]

WEB

ENB

RSTB

ADDRB[12:0]

CLKB

DIB[0]

Port B In8K-Bit Depth

Port A Out1-Bit Width

Port A In8K-Bit Depth

Two Independent Single-Port RAMs

• To access the lower RAM• Tie the MSB address bit to Logic Low

• To access the upper RAM• Tie the MSB address bit to Logic High

• Added advantage of True Dual-Port• No wasted RAM Bits

• Can split a Dual-Port 16K RAM into two Single-Port 8K RAM

• Simultaneous independent access to each RAM

19

Inference vs.

Instantiation

22

Generic

Inferred

RAM

23

Distributed versus Block RAM Inference

• Examples:1. Distributed RAM with asynchronous read

2. Distributed RAM with "false" synchronous read

3. Block RAM with synchronous read

4. Distributed dual-port RAM with asynchronous read

More excellent RAM examples from XST Coding Guidelines:http://toolbox.xilinx.com/docsan/xilinx4/data/docs/xst/hdlcode.html(Click on RAMs)

24

Distributed RAM with asynchronous read

25


LIBRARY ieee;USE ieee.std_logic_1164.all;USE ieee.std_logic_arith.all;USE ieee.std_logic_unsigned.all; entity raminfr is generic ( bits : integer := 32; -- number of bits per RAM word addr_bits : integer := 3); -- 2^addr_bits = number of words in RAM port (clk : in std_logic; we : in std_logic; a : in std_logic_vector(addr_bits-1 downto 0); di : in std_logic_vector(bits-1 downto 0); do : out std_logic_vector(bits-1 downto 0)); end raminfr;

26


architecture behavioral of raminfr is type ram_type is array (2**addr_bits-1 downto 0) of std_logic_vector (bits-1

downto 0); signal RAM : ram_type; begin process (clk) begin if (clk'event and clk = '1') then if (we = '1') then RAM(conv_integer(unsigned(a))) <= di; end if; end if; end process; do <= RAM(conv_integer(unsigned(a))); end behavioral;

27

Report from Synthesis

Resource Usage Report for raminfr Mapping to part: xc3s50pq208-5Cell usage:GND 1 useRAM16X4S 8 usesI/O ports: 69I/O primitives: 68IBUF 36 usesOBUF 32 usesBUFGP 1 use

I/O Register bits: 0Register bits not including I/Os: 0 (0%)

RAM/ROM usage summarySingle Port Rams (RAM16X4S): 8

Global Clock Buffers: 1 of 8 (12%)

Mapping Summary:Total LUTs: 32 (2%)

28

Report from Implementation

Design Summary:Number of errors: 0Number of warnings: 0Logic Utilization:Logic Distribution: Number of occupied Slices: 16 out of 768 2% Number of Slices containing only related logic: 16 out of 16 100% Number of Slices containing unrelated logic: 0 out of 16 0% *See NOTES below for an explanation of the effects of unrelated logicTotal Number of 4 input LUTs: 32 out of 1,536 2% Number used as 16x1 RAMs: 32 Number of bonded IOBs: 69 out of 124 55% Number of GCLKs: 1 out of 8 12%

29

Distributed RAM with "false" synchronous read

30


LIBRARY ieee;USE ieee.std_logic_1164.all;USE ieee.std_logic_arith.all;USE ieee.std_logic_unsigned.all; entity raminfr is generic ( bits : integer := 32; -- number of bits per RAM word addr_bits : integer := 3); -- 2^addr_bits = number of words in RAM port (clk : in std_logic; we : in std_logic; a : in std_logic_vector(addr_bits-1 downto 0); di : in std_logic_vector(bits-1 downto 0); do : out std_logic_vector(bits-1 downto 0)); end raminfr;

31



downto 0); signal RAM : ram_type; begin process (clk) begin if (clk'event and clk = '1') then if (we = '1') then RAM(conv_integer(unsigned(a))) <= di; end if;

do <= RAM(conv_integer(unsigned(a))); end if; end process; end behavioral;

32


Resource Usage Report for raminfr Mapping to part: xc3s50pq208-5Cell usage:FD 32 usesGND 1 useRAM16X4S 8 usesI/O ports: 69I/O primitives: 68IBUF 36 usesOBUF 32 usesBUFGP 1 use


RAM/ROM usage summarySingle Port Rams (RAM16X4S): 8



33


Design Summary:Number of errors: 0Number of warnings: 0Logic Utilization: Number of Slice Flip Flops: 32 out of 1,536 2%Logic Distribution: Number of occupied Slices: 16 out of 768 2% Number of Slices containing only related logic: 16 out of 16 100% Number of Slices containing unrelated logic: 0 out of 16 0% *See NOTES below for an explanation of the effects of unrelated logicTotal Number of 4 input LUTs: 32 out of 1,536 2% Number used as 16x1 RAMs: 32 Number of bonded IOBs: 69 out of 124 55% Number of GCLKs: 1 out of 8 12%

Total equivalent gate count for design: 4,355

34

Block RAM with synchronous read (read through)

35

Block RAM with synchronous read (read through)

LIBRARY ieee;USE ieee.std_logic_1164.all;USE ieee.std_logic_arith.all;USE ieee.std_logic_unsigned.all; library synplify; -- XST does not need this entity raminfr is generic ( bits : integer := 32; -- number of bits per RAM word addr_bits : integer := 3); -- 2^addr_bits = number of words in RAM port (clk : in std_logic; we : in std_logic; a : in std_logic_vector(addr_bits-1 downto 0); di : in std_logic_vector(bits-1 downto 0); do : out std_logic_vector(bits-1 downto 0)); end raminfr;

36

Block RAM with synchronous read (read through) cont'd


downto 0); signal RAM : ram_type; signal read_a : std_logic_vector(addr_bits-1 downto 0); attribute syn_ramstyle : string; -- XST does not need this attribute syn_ramstyle of RAM : signal is "block_ram"; -- XST does not need this

begin process (clk) begin if (clk'event and clk = '1') then if (we = '1') then RAM(conv_integer(unsigned(a))) <= di; end if;

read_a <= a; end if; end process; do <= RAM(conv_integer(unsigned(read_a)));end behavioral;

37


Resource Usage Report for raminfr Mapping to part: xc3s50pq208-5Cell usage:GND 1 useRAMB16_S36 1 useVCC 1 useI/O ports: 69I/O primitives: 68IBUF 36 usesOBUF 32 usesBUFGP 1 use


RAM/ROM usage summaryBlock Rams : 1 of 4 (25%)Global Clock Buffers: 1 of 8 (12%)


38


Design Summary:Number of errors: 0Number of warnings: 0Logic Utilization:Logic Distribution: Number of Slices containing only related logic: 0 out of 0 0% Number of Slices containing unrelated logic: 0 out of 0 0% *See NOTES below for an explanation of the effects of unrelated logic Number of bonded IOBs: 69 out of 124 55% Number of Block RAMs: 1 out of 4 25% Number of GCLKs: 1 out of 8 12%

39

Distributed dual-port RAM with asynchronous read

40


library ieee; use ieee.std_logic_1164.all; use ieee.std_logic_unsigned.all; use ieee.std_logic_arith.all; entity raminfr is generic ( bits : integer := 32; -- number of bits per RAM word addr_bits : integer := 3); -- 2^addr_bits = number of words in RAM port (clk : in std_logic; we : in std_logic; a : in std_logic_vector(addr_bits-1 downto 0); dpra : in std_logic_vector(addr_bits-1 downto 0); di : in std_logic_vector(bits-1 downto 0); spo : out std_logic_vector(bits-1 downto 0); dpo : out std_logic_vector(bits-1 downto 0)); end raminfr;

41


architecture syn of raminfr is type ram_type is array (2**addr_bits-1 downto 0) of std_logic_vector (bits-1

downto 0); signal RAM : ram_type; begin process (clk) begin if (clk'event and clk = '1') then if (we = '1') then RAM(conv_integer(unsigned(a))) <= di; end if; end if; end process; spo <= RAM(conv_integer(unsigned(a))); dpo <= RAM(conv_integer(unsigned(dpra))); end syn;

42


Resource Usage Report for raminfr Mapping to part: xc3s50pq208-5Cell usage:GND 1 useI/O ports: 104I/O primitives: 103IBUF 39 usesOBUF 64 usesBUFGP 1 useI/O Register bits: 0Register bits not including I/Os: 0 (0%)

RAM/ROM usage summaryDual Port Rams (RAM16X1D): 32



43


Design Summary:Number of errors: 0Number of warnings: 0Logic Utilization:Logic Distribution: Number of occupied Slices: 32 out of 768 4% Number of Slices containing only related logic: 32 out of 32 100% Number of Slices containing unrelated logic: 0 out of 32 0% *See NOTES below for an explanation of the effects of unrelated logicTotal Number of 4 input LUTs: 64 out of 1,536 4% Number used for Dual Port RAMs: 64 (Two LUTs used per Dual Port RAM) Number of bonded IOBs: 104 out of 124 83% Number of GCLKs: 1 out of 8 12%

44

Specification of memory types recognized by Synplify Pro

attribute syn_ramstyle : string;attribute syn_ramstyle of memory : signal is "block_ram";

attribute syn_ramstyle : string;attribute syn_ramstyle of memory : signal is “select_ram";

LUT-based Distributed Memory:

Block RAM Memory:

SIGNAL memory : vector_array;

45

Generic

Inferred

ROM

46


LIBRARY ieee;USE ieee.std_logic_1164.all;USE ieee.std_logic_arith.all;USE ieee.std_logic_unsigned.all; entity rominfr is generic ( bits : integer := 10; -- number of bits per ROM word addr_bits : integer := 3); -- 2^addr_bits = number of

words in ROM port (a : in std_logic_vector(addr_bits-1 downto 0); do : out std_logic_vector(bits-1 downto 0)); end rominfr;

47


architecture behavioral of rominfr is type rom_type is array (2**addr_bits-1 downto 0) of std_logic_vector

(bits-1 downto 0); constant ROM : rom_type := ("0000110001", "0100110100", "0100110110", "0110110000", "0000111100", "0111110101", "0100110100", "1111100111"); begin do <= ROM(conv_integer(unsigned(a))); end behavioral;

48


Resource Usage Report for rominfr

Mapping to part: xc3s50pq208-5Cell usage:VCC 1 useLUT2 2 usesLUT3 7 uses

I/O ports: 13I/O primitives: 13IBUF 3 usesOBUF 10 uses



49


Design Summary:Number of errors: 0Number of warnings: 0Logic Utilization: Number of 4 input LUTs: 9 out of 1,536 1%Logic Distribution: Number of occupied Slices: 5 out of 768 1% Number of Slices containing only related logic: 5 out of 5 100% Number of Slices containing unrelated logic: 0 out of 5 0% *See NOTES below for an explanation of the effects of unrelated logicTotal Number of 4 input LUTs: 9 out of 1,536 1% Number of bonded IOBs: 13 out of 124 10%

50

FPGA

specific memories

(Instantiation)

51

RAM 16x1 (1)

library IEEE;use IEEE.STD_LOGIC_1164.all;

library UNISIM;use UNISIM.all;

entity RAM_16X1_DISTRIBUTED is port(

CLK : in STD_LOGIC; WE : in STD_LOGIC; ADDR : in STD_LOGIC_VECTOR(3 downto 0); DATA_IN : in STD_LOGIC; DATA_OUT : out STD_LOGIC

);end RAM_16X1_DISTRIBUTED;

52

RAM 16x1 (2)

architecture RAM_16X1_DISTRIBUTED_STRUCTURAL of RAM_16X1_DISTRIBUTED is-- part used by the synthesis tool, Synplify Pro, only; ignored during

simulation attribute INIT : string; attribute INIT of RAM_16x1s_1: label is "0000";

------------------------------------------------------------------------

component ram16x1sgeneric(

INIT : BIT_VECTOR(15 downto 0) := X"0000");port(

O : out std_ulogic; -- note std_ulogic not std_logicA0 : in std_ulogic;A1 : in std_ulogic;A2 : in std_ulogic;A3 : in std_ulogic;D : in std_ulogic;WCLK : in std_ulogic;WE : in std_ulogic);

end component;

53

RAM 16x1 (3)

begin

RAM_16x1s_1: ram16x1s generic map (INIT => X"0000")port map

(O => DATA_OUT, A0 => ADDR(0), A1 => ADDR(1), A2 => ADDR(2), A3 => ADDR(3), D => DATA_IN, WCLK => CLK, WE => WE );

end RAM_16X1_DISTRIBUTED_STRUCTURAL;

54

RAM 16x8 (1)



entity RAM_16X8_DISTRIBUTED is port(

CLK : in STD_LOGIC; WE : in STD_LOGIC; ADDR : in STD_LOGIC_VECTOR(3 downto 0); DATA_IN : in STD_LOGIC_VECTOR(7 downto 0); DATA_OUT : out STD_LOGIC_VECTOR(7 downto 0)

);end RAM_16X8_DISTRIBUTED;

55

RAM 16x8 (2)

architecture RAM_16X8_DISTRIBUTED_STRUCTURAL of RAM_16X8_DISTRIBUTED is

-- part used by the synthesis tool, Synplify Pro, only; ignored during simulationattribute INIT : string;--attribute INIT of RAM_16x1s_1: label is "0000";



O : out std_ulogic;A0 : in std_ulogic;A1 : in std_ulogic;A2 : in std_ulogic;A3 : in std_ulogic;D : in std_ulogic;WCLK : in std_ulogic;WE : in std_ulogic);

end component;

56

RAM 16x8 (3)

begin

GENERATE_MEMORY:for I in 0 to 7 generate

RAM_16x1_S_1: ram16x1s generic map (INIT => X"0000")port map (O => DATA_OUT(I),

A0 => ADDR(0), A1 => ADDR(1), A2 => ADDR(2),

A3 => ADDR(3), D => DATA_IN(I), WCLK => CLK, WE => WE );

end generate;

end RAM_16X8_DISTRIBUTED_STRUCTURAL;

57

ROM 16x1 (1)



entity ROM_16X1_DISTRIBUTED is port( ADDR : in STD_LOGIC_VECTOR(3 downto 0);

DATA_OUT : out STD_LOGIC );

end ROM_16X1_DISTRIBUTED;

58

ROM 16x1 (2)

architecture ROM_16X1_DISTRIBUTED_STRUCTURAL of ROM_16X1_DISTRIBUTED is

-- part used by the synthesis tool, Synplify Pro, only; ignored during simulationattribute INIT : string;attribute INIT of rom16x1s_1: label is "F0C1";



O : out std_ulogic;A0 : in std_ulogic;A1 : in std_ulogic;A2 : in std_ulogic;A3 : in std_ulogic;D : in std_ulogic;WCLK : in std_ulogic;WE : in std_ulogic);

end component;

signal Low : std_ulogic := '0';

59

ROM 16x1 (3)

begin

rom16x1s_1: ram16x1s generic map (INIT => X"F0C1")

port map(O=>DATA_OUT,

A0=>ADDR(0), A1=>ADDR(1), A2=>ADDR(2), A3=>ADDR(3), D=>Low, WCLK=>Low, WE=>Low

);

end ROM_16X1_DISTRIBUTED_STRUCTURAL;

60

Block RAM library components

Component Data Cells Parity Cells Address Bus Data Bus Parity Bus

Depth Width Depth Width

RAMB16_S1 16384 1 - - (13:0) (0:0) -

RAMB16_S2 8192 2 - - (12:0) (1:0) -

RAMB16_S4 4096 4 - - (11:0) (3:0) -

RAMB16_S9 2048 8 2048 1 (10:0) (7:0) (0:0)

RAMB16_S18 1024 16 1024 2 (9:0) (15:0) (1:0)

RAMB16_S36 512 32 512 4 (8:0) (31:0) (3:0)

61

Component declaration for BRAM (1)

-- Component Declaration for RAMB16_{S1 | S2 | S4} -- Should be placed after architecture statement but before begin keyword component RAMB16_{S1 | S2 | S4} -- synthesis translate_off generic ( INIT : bit_vector := X"0"; INIT_00 : bit_vector := X"0000000000000000000000000000000000000000000000000000000000000000"; ………………………………… INIT_3F : bit_vector := X"0000000000000000000000000000000000000000000000000000000000000000"; SRVAL : bit_vector := X"0"; WRITE_MODE : string := "WRITE_FIRST"); -- synthesis translate_on port (DO : out STD_LOGIC_VECTOR (0 downto 0) ADDR : in STD_LOGIC_VECTOR (13 downto 0); CLK : in STD_ULOGIC; DI : in STD_LOGIC_VECTOR (0 downto 0); EN : in STD_ULOGIC; SSR : in STD_ULOGIC; WE : in STD_ULOGIC); end component;

62

Genaral template of BRAM instantiation (1)

-- Component Attribute Specification for RAMB16_{S1 | S2 | S4} -- Should be placed after architecture declaration but before the begin

keyword -- Put attributes, if necessary -- Component Instantiation for RAMB16_{S1 | S2 | S4} -- Should be placed in architecture after the begin keyword RAMB16_{S1 | S2 | S4}_INSTANCE_NAME : RAMB16_S1 -- synthesis translate_off generic map ( INIT => bit_value, INIT_00 => vector_value, INIT_01 => vector_value, …………………………….. INIT_3F => vector_value, SRVAL=> bit_value, WRITE_MODE => user_WRITE_MODE) -- synopsys translate_on port map (DO => user_DO, ADDR => user_ADDR, CLK => user_CLK, DI => user_DI, EN => user_EN, SSR => user_SSR, WE => user_WE);

63

INIT_00 : BIT_VECTOR := X"014A0C0F09170A04076802A800260205002A01C5020A0917006A006800060040";INIT_01 : BIT_VECTOR := X"000000000000000008000A1907070A1706070A020026014A0C0F03AA09170026";INIT_02 : BIT_VECTOR := X"0000000000000000000000000000000000000000000000000000000000000000";INIT_03 : BIT_VECTOR := X"0000000000000000000000000000000000000000000000000000000000000000";……………………………………………………………………………………………………………………………………INIT_0F : BIT_VECTOR := X"0000000000000000000000000000000000000000000000000000000000000000")

0000F0

0000F1

0000F2

0000F3

0000F4

0000FE

0000FF

INIT_0FADDRESS

002610

091711

03AA12

0C0F13

014A14

00001E

00001F

INIT_01ADDRESS

004000

000601

006802

006A03

091704

0C0F0E

014A0F

INIT_00ADDRESS

Addresses are shown in red and

data corresponding to the same

memory location is shown in black

ADDRESSDATA

Initializing Block RAMs 256x16

64

Component declaration for BRAM (2)VHDL Instantiation Template for RAMB16_S9, S18 and S36 -- Component Declaration for RAMB16_{S9 | S18 | S36} component RAMB16_{S9 | S18 | S36} -- synthesis translate_off generic ( INIT : bit_vector := X"0"; INIT_00 : bit_vector :=

X"0000000000000000000000000000000000000000000000000000000000000000"; INIT_3E : bit_vector :=

X"0000000000000000000000000000000000000000000000000000000000000000"; INIT_3F : bit_vector :=

X"0000000000000000000000000000000000000000000000000000000000000000"; INITP_00 : bit_vector :=

X"0000000000000000000000000000000000000000000000000000000000000000"; INITP_07 : bit_vector :=

X"0000000000000000000000000000000000000000000000000000000000000000"; SRVAL : bit_vector := X"0"; WRITE_MODE : string := "WRITE_FIRST"; ); -- synthesis translate_on port (DO : out STD_LOGIC_VECTOR (0 downto 0); DOP : out STD_LOGIC_VECTOR (1 downto 0); ADDR : in STD_LOGIC_VECTOR (13 downto 0); CLK : in STD_ULOGIC; DI : in STD_LOGIC_VECTOR (0 downto 0); DIP : in STD_LOGIC_VECTOR (0 downto 0); EN : in STD_ULOGIC; SSR : in STD_ULOGIC; WE : in STD_ULOGIC); end component;

65

-- Component Attribute Specification for RAMB16_{S9 | S18 | S36} -- Component Instantiation for RAMB16_{S9 | S18 | S36} -- Should be placed in architecture after the begin keyword RAMB16_{S9 | S18 | S36}_INSTANCE_NAME : RAMB16_S1 -- synthesis translate_off generic map ( INIT => bit_value, INIT_00 => vector_value, . . . . . . . . . . INIT_3F => vector_value, INITP_00 => vector_value, …………… INITP_07 => vector_value SRVAL => bit_value, WRITE_MODE => user_WRITE_MODE) -- synopsys translate_on port map (DO => user_DO, DOP => user_DOP, ADDR => user_ADDR, CLK => user_CLK, DI => user_DI, DIP => user_DIP, EN => user_EN, SSR => user_SSR, WE => user_WE);

Genaral template of BRAM instantiation (2)

66

Block RAM Waveforms – WRITE_FIRST

67

Block RAM Waveforms – READ_FIRST

68

Block RAM Waveforms – NO_CHANGE

ece 448 – fpga and asic design with vhdl lecture 10 memories (ram/rom)

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