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reduction nand operator in verilog Verilog keywords also include compiler directives, and system tasks and functions. The result is a single bit boolean value. ppt Author: phd Created Date: 10/12/2004 12:49:50 PM CSCI 320 Handbook on Verilog Page 4 1. Verilog includes the C conditional expression (question mark - colon) construct. For the FPGA, division and multiplication are very expensive, and sometimes we cannot synthesize division. However, the inputs to both of these operators can be either single bit or vector types. The operators included in Reduction operation are: & (reduction AND) | (reduction OR) ~& (reduction NAND) ~| (reduction NOR) ^ (reduction XOR) ~^ or ^~(reduction XNOR) 6. Elect. There can be an module without inputs or outputs. They Variables in Verilog may be declared as integers or real. Conditional Operator: The conditional operator evaluates one of the two expressions based on the condition which is present in the operator. They operate on all of In the article, Reduction Operators In Verilog, we will discuss the topics of Verilog reduction operators. SUNY –New Paltz. Unary operators can operate on only one operand. Operators perform an operation on one or more operands within an expression. The logic performed on the bit-vectors behaves the same way that normal AND, NAND, OR, NOR, XOR, and XNOR Gates behave inside of an FPGA. 2. accellera. An expression combines operands with appropriate operators to produce the desired functional expression. Relational operators have a lower precedence than arithmetic operators and all relational operators have the same precedence. com An XOR built from four NAND gates. These also return a single-bit value. They should not be used as identifiers. Verilog has large number of operators. Verilog Operator Precendence. 2. 5. If a = 5’b10101, b = 4’b0011, c = 3’bz00 and d = 3’bx011. Arithmetic * Multiply / Division + Add - Subtract % Modulus + Unary plus - Unary minus: Logical ! Logical negation && Logical and || Logical or: Relational > Greater than < Less than >= Greater than or equal <= Less than or equal: Equality == Equality!= inequality: Reduction ~ Bitwise negation ~& nand | or ~| nor ^ xor ^~ xnor ~^ xnor : Shift >> Right shift << I’m using MyHDL on some of my small projects, and I want to implement some simple functions using width expansion and reduced unary operator, like following snippets as in verilog: // svalid: 1-bit; en, dready: 4-bit // width expansion assign dvalid = {NUM_W{svalid}} & en; // reduced or assign sready = | (dready & en) But i dont have a clue how to code them using MyHDL. Reduction Operators D N A n o i t c u d e &R ~& Reduction NAND Microsoft PowerPoint - Verilog 2. Verilog Support. The packing or unpacking can be done on a matching data-type or by type-casting to a particular data-type that match the Widths. 6. Parameterizable models VHDL. Verilog: A common language for industry HDL is a common way for hardware design Verilog VHDL Verilog is widely adopted in Taiwan’s industry VHDL is applied by American Military Realization of HDL into hardware FPGA prototype Cell based design 2008/3/12 VLSI Digital Signal Processing 4 Verilog: A common language for industry Design steps Reduction Logical Unary operators that perform bit-wise operations on a single operand, reduce it to one bit // Uses Verilog builtin nand function A Simple Dataflow Design. Bit-wise operators. For example, the following module describes an 8-input AND gate with inputs A[0], A[1], A[2], …, A[7]. The following table briefs the operator and its examples. logical negation & bit-wise and (also unary reduction and) ~& unary reduction nand | bit-wise or (also unary reduction or, event or) ~| reduction nor ^ bit-wise exclusive or (unary reduction xor) ~^ bit-wise equivalence (^~) (also unary reduction xnor) ~ bit-wise complement >> bit-wise logical right shift << bit-wise logical left shift >>> bit-wise arithmetic right shift <<< bit-wise arithmetic left shift ? : condition ? value-if-true : value-if-false ? ~&a NAND |a OR ~|a NOR ^a XOR ~^a ^~a XNOR Reduction Note distinction between ~a and !a when operating on multi-bit values 6. They take one operand and perform a bit-by-next-bit operation,starting with the two leftmost bits, giving a 1-bit result. 6. Operator Name . 1. 6. 12. Wires and net declarations; Logic bitwise primitives; Reduction; Concatenation and Replication; Shifting; Rotation; Conditional expressions; Operator precedence; Combinatorial always blocks; If/Else (1) If/Else (2) Conditional example: 4-bit decoder; Conditional example: implementation; Conditional example: improved Operator Precedence If no parentheses are used to separate operands then Verilog uses the following rules of precedence. Verilog provides data types such as reg and wire for actual hardware description. Operators are described in detail in “Operators” on p. If there are the characters z and x the result can be a known value. Lexicon. module reductTest; reg [3:0] a, b ,c; initial begin a = 4'b1111; b = 4'b0101; c = 4'b0011; $displayb(& a); // bitwise and, (same as 1&1&1&1), evaluates to 1 $displayb(| b); // bitwise or, (same as 0|1|0|1), Verilog - Operators Reduction Operators I and(&), nand(˘&), or(j), nor(˘j) xor(^), xnor(^˘,˘^) I Operates on only one operand I Performs a bitwise operation on all bits of the operand I Returns a 1-bit result I Works from right to left, bit by bit //let x = 4’b1010 &x //equivalent to 1 & 0 & 1 & 0. Arithmetic Operators. They take two values and compare (or otherwise operate on) them to yield a third result. 3. verilog +maxdelays test. size. 5. Operator Type Symbol Operation Performed Arithmetic + Add - Subtract * Multiply / Divide % Modulus Logical ! Logical negation && Logical and || Logical or Unary(Reduction) operator. 9. This page contains Verilog tutorial, Verilog Syntax, Verilog Quick Reference, PLI, modelling memory and FSM, Writing Testbenches in Verilog, Lot of Verilog Examples and Verilog in One Day Tutorial. When used in a number, the question mark (?) character is the Verilog alternative for the z character. In the article, Conditional Operator In Verilog, we will discuss the topics of the Verilog conditional operator. In this example the module’s behavior is specified using Verilog’s built-in Boolean modules: not, buf, and, nand, or, nor, xor, Unary Reduction Operators • Unary reduction operators produce a single bit result from applying the operator to all of the bits of the operand. The operator precedence is: Reduction AND: One: Reduction ~& Reduction NAND: One: Reduction | Reduction OR: One: Reduction ~| Reduction NOR: One: Reduction ^ Reduction XOR: One: Reduction ^~ Reduction XNOR: One: Shift >> Right Shift: Two: Shift << Left Shift: Two: Concatenation { } Concatenation: Can be of any numbers: Replication { { } } Replication: Can be of any numbers: Conditional? : Conditional: Three For example, assign, case, while, wire, reg, and, or, nand, and module. If either of the operands is X or Z, then the result will be X. If there are the characters z and x the result can be a known value. 11 to the latest SystemVerilog IEEE Std 1800-2012 in § 11. A Hardware Description Language is a language used to describe a digital system, for example, a computer or a component Verilog HDL Basics. unary operators. ENDS X1 A B I1 Vdd 0 NAND X2 A I1 I2 Vdd 0 NAND X3 B I1 I3 Vdd 0 NAND X4 I2 I3 Y Vdd 0 NAND Vss Y Vdd A B X1 X2 X3 X4 A B I1 I2 I3 Y OPERATORS . reduction operator cannot aprove verilog's advantage vs. Binary Arithmetic Operators . 2. Some examples are assign, case, while, wire, reg, and, or, nand, and module. 2 Unary Reduction Operators Reduction Operators ¶ These operators reduces the vectors to only one bit. It should be mentioned that these brackets can also be used to do concatenation in Verilog, but that is for another example. SUBCKT NAND A B Y Vdd Vss M1 Y A Vdd Vdd P M2 Y B Vdd Vdd P M3 Y A X Vss N M4 X B Vss Vss N. & Operators are described in detail in “Operators” on p. Numbers in Verilog (iii) • If . is ommitted too . Verilog – created in 1984 by Philip Moorby of Gateway Design Automation (merged with Cadence) • IEEE Standard 1364-1995/2001/2005 • Based on the C language • Verilog-AMS – analog & mixed-signal extensions • IEEE Std. 1 Carry Lookahead Notes: Verilog Part 3 The Carry lookahead is given for solution of timing problems for carry propagation. INTRODUCTION Verilog HDL is a Hardware Description Language (HDL). Some examples areassign, case, while, wire, reg, and, or, nand, and module. The Verilog reduction operators are used to convert vectors to scalars. Verilog Operators. Output of this operators is of only one bit (“0” or “1”). Unknown bits are treated as described before. Verilog describes a digital system as a set of modules. At each step of this recursive calculation the logical bit-wise operation is performed on the result of a previous operation and on the next bit of the operand. The operators used in building these equations can use either be the standard operators that are provided in the generation language, or they can use the language independent operators shown in the Syncad column. –~negation Verilog VHDL –&and y = a & b; y = a AND b; –|inclusive or y = a | b; y = A OR b; –^exclusive or y = a ^ b; y = a XOR b; – y = ~(a & b); y = A NAND b; – y = ~ a; y = NOT a; • Reduction (no direct equivalent in VHDL) – Accept single bus and return single bit result. Verilog Keywords These are words that have special meaning in Verilog. Verilog primitives include gates, e. It is normally a good idea to use parentheses to make expressions readable. Notice how the verilog code gets simplified by the use of the udp tables/ Streaming Operator : Streaming operator ‘<<‘ & ‘>>’ are used to pack or unpack the data in specified order. 2. For example, if y is 1011_0001, the reduction and operations produces &y = 0. module reduction_operators; reg[5:0] X; initial begin X = 4'b1010; $display ("&X = %b", &X); $display ("|X = %b", |X); $display ("^X= %b", ^X); $display("~^X = %b", ~(^X)); //XNOR of X end endmodule. 4. , nand, as well as pass transistors (switches). Verilog has six reduction operators, these operators accept a single vectored (multiple bit) operand, performs the appropriate bit-wise reduction on all bits of the operand, and returns a single bit result. Here is the full Verilog code for the NAND gate using behavioral modeling: module NAND_2_behavioral (output reg Y, input A, B); always @ (A or B) begin if (A == 1'b1 & B == 1'b1) begin Y = 1'b0; end else Y = 1'b1; end endmodule Reduction operator performs logical AND operation between all the bits of a single vector. However, when even one of the operands is a vector, the results may differ. 6. Operators which return a True/False result will return a 1-bit value where 1 is True, 0 is False, and X is indeterminate. Reduction Operators Reduction operators operate on all the bits of an operand vector and return a single-bit value. Unary Reduction Operators Unary reduction operators produce a single bit result from applying the operator to all of the bits of the operand. is ommitted it – is inferred from the . Operator Name & AND reduction | OR reduction ^ XOR reduction ~& NAND reduction ~| NOR reduction ~^ XNOR reduction Other Operators Unary Reduction Operators •Unary reduction operators produce a single bit result from applying the operator to all of the bits of the operand. 1. 111 Fall 2015 Lecture 3 17 Integer Arithmetic • Verilog’s built-in arithmetic makes a 32-bit adder easy: • A 32-bit adder with carry-in and carry-out: module add32 (input[31:0] a, b, output[31:0] sum); assign sum = a + b; endmodule 5. Examples include >,+, ~, &,!=. Levels of Verilog Coding Slide 8 Module basics Data Types Verilog Operators Arithmetic Operators More operators …More operators …Operators (cont’d. . • Operator Name • & AND reduction • | OR reduction • ^ XOR reduction • ~& NAND reduction • ~| NOR reduction • ~^ XNOR reduction See full list on tutorialspoint. Names for the instances are b[1] and b[0]. Equivalent to (b[3:0] != 4'h0) ^ c[2:0] // XOR: c[2]^c[1]^c[0] Verilog Operators Cont’ Operator Type Operator Symbol Operation Performed Number of Operands Bitwise ~ & | ^ ^~ or ~^ bitwise negation bitwise and bitwise or bitwise xor bitwise xnor one two two two two Reduction & ~& | ~| ^ ^~ or ~^ reduction and reduction nand reduction or reduction nor reduction xor reduction xnor one one one one one one Shift >> << >>> <<< Right shift Left shift Arithmetic right shift Arithmetic left shift two two two two Concatenation {} Concatenation Any number "Useful Operators shift operation << >> shift left shift right 2. 6. 2. Reduction operators are unary. The operators start its operation from right and after evaluation of every bits to left it gives a single bit as the final result. 6. The bit-wise operators calculate each bit of results by evaluating the logical expression on a pair of corresponding operand bits. org Note: Attention is called to the possibility that implementation of this standard may require use of subject matter covered by patent rights. These are the unary (one argument) form of the bit-wise operators above. Verilog supports the C ternary operator, as in Reduction operators let you take all wires of a bus, connect them to a single multi-input OR, XOR, NAND and NOR wire u = |a; // Reduction op | yields u = 1’b1; short for (a > 0) wire v = ~|a; // Reduction op ~| yields v = 1’b0; short for (a == 0) wire w = &a; // Reduction op & yields w = 1’b0; This tests for all ones wire a_gt_b = (a > b); // Yields a_gt_b = 1’b1; • Operators can also be used with reg data type • Reduction operators act on each bit of a single input vector • &(4’b0101) = 0 & 1 & 0 & 1 = 1’b0 • Logical operators return one-bit (true/false) results • !(4’b0101) = 1’b0 ~a NOT a & b AND a | b OR a ^ b XOR a ~^ b a ^~ b XNOR Bitwise Logical !a NOT a && b AND a || b OR a == b a != b [in]equality Reduction Operators Reduction operators are used to perform bitwise operation on the same operand bit by bit and return the single bit value. Operation Performed. 6. The Eda playground example for the Reduction Operator in Verilog: Verilog Reduction Operators. List of Operators provided by Verilog The negation operator (!) turns a nonzero or true value of the operand into 0, zero or false value into 1, and ambiguous value of operator results in x (unknown value). edu) things to add to cheat sheet. Verilog Operator: Name. module <module_name>(<port_names>); endmodule Example: module Nand(q, a, b); output q; input a, b; nand (q, a, b); endmodule Arithmetic Operators + addition - subtraction Reduction Operators & reduce via AND ~& reduce via NAND | reduce via OR ~| reduce via NOR ^ reduce via XOR ^~ reduce via XNOR Shift Operators >> shift right << shift left >>> arithmetic shift right Relational Operators == equal!= not equal > greater than >= greater than or equals < less than <= less than or equals The code for the same is given in Multiplexer using conditional operator. These declarations are intended only for use in test code. Joined Jan 6, 2003 Messages 1,238 Helped 50 nand #(1,2) gate1 (y, i1, i2); This is a two-input nand gate instance with two delays specified. In both instances, the output of these operators are a vector type. From Verilog's original IEEE Std 1364-1995 in § 4. Operators are described in detail in “Operators” on p. 1. Feb 19, 2007 #9 omara007 Advanced Member level 4. Simulation log &X = 0 |X = 1 ^X= 0 ~^X = 0 The reduction operators areand,nand,or,nor,xorxnorand an alternativexnor. The reduction operators can do AND, OR, and XOR of the bits of a vector, producing one bit of output: & a[3:0] // AND: a[3]&a[2]&a[1]&a[0]. 1 course point (on 100) for each idea accepted; cumulative no more than 5 for a student. Numbers You can specify constant numbers in decimal, hexadecimal, octal, or binary format. g. Reduction operators imply a multiple-input gate acting on a single bus. The reduction operation is performed bitwise from right to left on the bits of the same word. All these operators will come under unary operators. As an example, consider the reduction operation &x where x is a 4-bit number. wisc. For example, the reduction AND operator takes the AND value of all the bits of the operand and returns a 1-bit result. The final types of verilog operator which we can use are the concatenation and replication operators. 2 Operator reduction operation ~ & | ^ ~& ~| ~^ negation and or exclusive-or nand nor exclusive-nor module Shl_4bit_RTL (y, x, c) ; input [3:0]x ; input [1:0]c ; output [3:0]y ; assign y = x << c; endmodule module And4_RTL (y, x) ; input [3:0]x ; output y ; assign y = &x ; endmodule Reduction Operators These are unary operators which create a single bit value for a data word of multiple bits. Verilog, standardized as IEEE 1364, is a hardware description language (HDL) used to model electronic systems. Bitwise - Operation on individual bits of registers. 7 Other Operators The conditional operator operates much like in the language C. Operator Name Comments === Case equality The bitwise comparison includes comparison of x and z values. Also discussed is the verilog code implementation. ” & (and)” If all bits of variable are ” 1 “, then only output will be ” 1 “. Verilog has built-in primitives like logic gates, transmission gates and switches. The Verilog reduction operators are • ReductionAND (&) • ReductionOR (|) • ReductionNAND (~&) • ReductionNOR (~|) • ReductionXOR (^) Verilog Bitwise Operator: but we have used primitive gates in this example. 2 Arithmetic All arithmetic is signed. Relational Operators Verilog Operators (3) Built-in arithmetic operators treat vectors as unsigned integers; leftmost bit of a vector is MSB Shift operator shifts the 1st operand by a number of positions given by the 2nd operand – Example: 8'b11010011<<3 gives 8'b10011000 Boolean reduction operators take a single vector operand and collapse it to a 1-bit result Verilog Operator Precendence. Reduction Operators Reduction operators take one operand and return a single bit. It is most commonly used in the design and verification of digital circuits at the register-transfer level of abstraction. 8) for CS552 - Spring 2013 1 Developed by: Vinay Gangadhar, Cherin Joseph & Prof. If a = 5’b10101, b = 4’b0011, c = 3’bz00 and d = 3’bx011 . ) Operators (last one!) Verilog modeling Always Blocks Always Blocks (Combinational) Always Blocks (Sequential) Continuous Assignment Questions References Verilog values are unsigned C[4:0] = A[3:0] + B[3:0]; if A = 0110 (6) and B = 1010(–6), then C = 10000 ( not 00000) B is zero-padded, not sign-extended CSE370, Lecture 7 14 Operators Similar to C operators CSE370, Lecture 7 15 Two abstraction mechanisms Modules More structural Heavily used in 370 and “real” Verilog code Functions Verilog History • Gateway Design Automation – Phil Moorbr in 1984 and 1985 • Verilog-XL, “XL algorithm”, 1986 – Fast gate-level simulation • Verilog logic synthesizer, Synopsys, 1988 – Top-down design methodology • Cadence Design Systems acquired Gateway, 1989 – A proprietary HDL • Open Verilog International (OVI), 1991 TABLE IU: Verilog Common Operators Operator U 0 1 reductical XNOR ( [?] + से Name Functionul Group bit select parenthesis reduction AND reduction reduction OR reduction reduction NAND reduction reduction NOR reduction www reduction XOR reduction reduction - Conculenation concatenation Pandan replication replication multiply withirietic Language Specific Operators. An XOR built from four NAND gates. // Verilog code for AND-OR-INVERT gate module AOI (input A, B, C, D, output F); assign F = ~((A & B) | (C & D)); endmodule // end of Verilog code ‘&’ for AND, ‘|’ for OR, ‘^’ for XOR ‘^~’ for XNOR, ‘&~’ for NAND. If any bit is unknown ('x') then result is unknown. Equivalent to (a[3:0] == 4'hf) | b[3:0] // OR: b[3]|b[2]|b[1]|b[0]. VHDL has the mod operator that is not found in Verilog. 3. VHDL. Both of these verilog operators are show in the table below. Functional Group [ ] bit-select or part-select ( ) parenthesis! ~ & | ~& ~| ^ ~^ or ^~ logical negation negation reduction AND reduction OR reduction NAND reduction NOR reduction XOR reduction XNOR: logical bit-wise reduction reduction reduction reduction reduction reduction + – unary (sign) plus unary (sign) minus: arithmetic arithmetic { } concatenation: concatenation {{ }} Verilog Relational Operators An expression with the relational operator will result in a 1 if the expression is evaluated to be true, and 0 if it is false. ENDS X1 A B I1 Vdd 0 NAND X2 A I1 I2 Vdd 0 NAND X3 B I1 I3 Vdd 0 NAND X4 I2 I3 Y Vdd 0 NAND Vss Y Vdd A B X1 X2 X3 X4 A B I1 I2 I3 Y As one would expect, |, ^, ~&, and ~| reduction operators are available for OR, XOR, NAND, and NOR as well. Reduction unary NAND and NOR operators operate as AND and OR respectively, but with their outputs negated. MODEL N NMOS. A loop statement can be used in VHDL to perform the same operation as a Verilog unary reduction operator. For example, &A will AND all the bits of A. Also discussed is the verilog code implementation. Streaming Operator : Streaming operator ‘<<‘ & ‘>>’ are used to pack or unpack the data in specified order. Each module has an interface and a description off its contents. The logic performed on the bit-vectors behaves the same way that normal AND, NAND, OR, NOR, XOR, and XNOR Gates behave inside of an FPGA. 9: The unary reduction operators shall perform a bit-wise operation on a single Operator Type Operator Symbol Operation # of Operands Reduction & Reduction and 1 ~& Reduction nand 1 | Reduction or 1 ~| Reduction nor 1 ^ Reduction xor 1 ~^ Reduction xnor 1 S. Reduction Operator: All the bits of an operand vector will be operated in this reduction operator and return a single bit either 0 or 1. Results in 1’b0 |x //equivalent to 1 | 0 | 1 | 0. Verilog - 19 Tri-State Buffers • ‘Z’ value is the tri-stated value • This example implements tri-state drivers driving BusOut module tstate (EnA, EnB, BusA, BusB, BusOut); Operators are one, two and sometimes three characters used to perform operations on variables. Verilog Keywords These are words that have special meaning in Verilog. MODEL P PMOS. Verilog Keywords These are words that have special meaning in Verilog. Modules usually have named, directional ports (specified as input, output or inout) which are used to communicate with the module. 2. The packing or unpacking can be done on a matching data-type or by type-casting to a particular data-type that match the Widths. However, real and integer operands may be signed. Verilog Synthesizable Operators Support; Verilog NON-Synthesizable Operator Support; Verilog Synthesizable Keyword Support; Verilog NON-Synthesizable Keyword Support; C Functions support; Verilog Synthesizable preprocessor Keywords Support; Syntax; Contributing; Regression Tests; Verify Script; TESTING ODIN II; ABC . The majority of operators are the same between the two languages. 2. 3 Descriptive Style 2. The instance name is gate1 and there is no strength specified. This result is calculated by recursively applying bit-wise operation on all bits of the operand. They should not be used as identifiers. Verilog Operator Name Functional Group [ ] bit-select or part-select ( ) parenthesis ! ~ & | ~& Reduction Operators The unary reduction operators shall perform a bit-wise operation on a single operand to produce a single bit result. They should be sent to the Verilog-AMS e-mail reflector v-ams@lists. They operate on all of the bits in a vector to convert the answer to a single bit. Verilog Cheat Sheet (version 0. g. 3. The reduction operator produces a 1-bit result. •Operator Name •& AND reduction •| OR reduction •^ XOR reduction •~& NAND reduction •~| NOR reduction •~^ XNOR reduction Reduction Operators The Verilog reduction operators are used to convert vectors to scalars. Refer to Cadence Verilog-XL Reference Manual for a complete listing of Verilog keywords. All bits must match for equality. module Reduction (A, Y1, Y2, Y3, Y4, Y5, Y6); See full list on alchitry. Gate Level Modelling. For example, &A will AND all the bits of A. Recall that a multi-bit XOR performs parity, returning true if an odd number of inputs are true. The difference between reg and wire is whether the variable is given its value by behavioral (reg) or structural (wire) Verilog code. Here is an excerpt from IEEE Std 1800-2012 § 11. com Verilog offers a feature called reduction operator for the logic operations and, nand, or, nor, xor and xnor. The delay control is just a way of adding a delay between the time the simulator encounters the statement and when it actually executes it. The == and != operators return X if either argument is X, while the === and !== opera-tors can compare to the value X itself. 4. EE577b Verilog for Behavioral Modeling Nestoras Tzartzanis 21 February 3, 1998 Reduction Operators • Reduction operators are unary • They perform a bit-wise operation on a single operand to produce a single bit result • Reduction unary NAND and NOR operators operate as AND and OR respectively, but with their outputs negated Some*Verilog*Operators Reduction*Operators ~ negation & bitwise*AND | bitwise*OR ~& bitwise*NAND ~| bitwise*NOR ^ bitwise*XOR ~^ bitwise*XNOR ^~ bitwise*XNOR Arithmetic*Operators + unary*(sign)*plus-unary*(sign)*minus + binary*plus*(add)-binary*minus*(sub) * multiply / divide % modulus Logical*Operators! logical*negation == logical*equality!= logical*inequality && logical*AND Operator Name Comments & AND reduction | OR reduction ^ XOR reduction ~& NAND reduction ~| NOR reduction ~^ XNOR reduction 2. MODEL P PMOS. SUBCKT NAND A B Y Vdd Vss M1 Y A Vdd Vdd P M2 Y B Vdd Vdd P M3 Y A X Vss N M4 X B Vss Vss N. Reduction Operators¶ These operators reduces the vectors to only one bit. Verilog does have very useful unary reduction operators that are not in VHDL. Reduction operators are the unary form of the bitwise operators and operate on all the bits of an operand vector. For example, &A will AND all the bits of A. For example, the four bits of A are ANDed together to produce Y1. They may be scalar, vector, or bit selects of a vector. Verilog has special syntax restriction on using both reduction and bitwise operators within the same expression — even though reduction operator has higher precedence, parentheses must be used to avoid confusion with a logical operator. decimal is assumed – 15 = <size>’d 15 Suggestions for improvements to the Verilog-AMS Language Reference Manual are welcome. Operators • Bitwise – ~ negation Verilog VHDL – & and y = a & b; y = a AND b; – | inclusive or y = a | b; y = A OR b; – ^ exclusive or y = a ^ b; y = a XOR b; – y = ~(a & b); y = A NAND b; – y = ~ a; y = NOT a; • Reduction (no direct equivalent in VHDL) – Accept single bus and return single bit result • & and y = & a_bus; • ~& nand • | or y = | a_bus; Reduction operator in verilog Verilog Example Code of Reduction Operators,are used to convert vectors to scalars. The Verilog replication operator is the open and close brackets {, }. The event expression allows the st Operators are one, two and sometimes three characters used to perform operations on variables. Operators Division and modulus operators for variables Case equality and inequality operators (=== and !==) Gate-Level Constructs pullup, pulldown, tranif0, tranif1, rtran, rtranif0, rtranif1 Miscellaneous Constructs Compiler directives like ‘ifdef, ‘endif, and ‘else Hierarchical names within a module reduction operators. Some examples are assign, case, while, wire, reg, and, or, nand, and module. Recall that a multi-bit XOR performs parity, returning true if an odd number of inputs are true. ” | (or)” Operator Type. NOTE: when executed on a single bit operands, the results of bitwise and logical operators are the same. They operate on all of the bits in a vector to convert the answer to a single bit. They The operators in Verilog are similar to those in the C programming language. or #1 b[1:0] (y, i1, i2, i3, i4); This is two instances of two four-input or gates with one delay specified. The operands may be either net or register data types. 2. 4 Other Operators The conditional operator ?: works like the same operator in C or Java and is very useful for describing multiplexers. Bitwise - Operation on individual bits of registers. Symbol Operator &, ~& reduction and, nand |, ~| reduction or, nor ^, ~^, ^~ reduction xor, xnor Reduction Logical Unary operators that perform bit-wise operations on a single operand, reduce it to one bit // Uses Verilog builtin nand function Verilog Operators • Arithmetic operators *, /, +, -, % • Logical operators! logical negation && logical AND | | logical OR • Relational operators >, <, >=, <=, ==, != • Bitwise operators ~, &, |, ^, ~^ CAD for VLSI 28 • Reduction operators (operate on all the bits within a word) &, ~&, |, ~|, ^, ~^ accepts a single word operand and produces a single bit as output • Shift operators >>, << • Concatenation { } Reduction Operators module Reduce ( input [3:0] A, B, output X, Y, Z ); // A, B are input vectors, X, Y, Z are 1-bit outputs // X = A[3] | A[2] | A[1] | A[0]; assign X = |A; // Y = B[3] & B[2] & B[1] & B[0]; assign Y = &B; // Z = X & (B[3] ^ B[2] ^ B[1] ^ B[0]); assign Z = X & (^B); endmodule Operators. Binary arithmetic operators operate on two operands. In some cases, languages do not have an operator to represent the operation described. Same as “AND GATE”. 11. Negative numbers are represented in 2's complement form. 4. 4. module Reduction (A, Y1, Y2, Y3, Y4, Y5, Y6); input [3:0] A; Here’s the code for understanding how reduction operator is described in Verilog. Reduction operators imply a XOR, NAND, and NOR /* an array of inverters */ module invA4 (input logic [3:0] a, Verilog Operators and Operator Precedence Reduction operator are described in the Reduction operators section all version of the LRM. 2 4-bit Full Adder The dataflow 4-bit Full Adder using the dataflow operators is given in Full Adder using Data Flow Operators. value . Palnitkar, “Verilog HDL: A Guide to Digital Design and Synthesis”, Sun Microsystems, 1996 10 Performs operation on all bits Verilog HDL:Digital Design and Modeling //module to illustrate the use of reduction operators module reduction1 (a //reduction NAND red_or = |a, //reduction Operators in Verilog are the same as they are in other programming languages. Operator Symbol. 4 Other Operators The conditional operator ?: works like the same operator in C or Java and is very useful for describing multiplexers. Comparisons can have two different semantics in the presence of X values. A ternary operator has two operator characters that separate three operands. Verilog Operators ~ bit-wise NOT & bit-wise AND | bit-wise OR ^ bit-wise XOR ^~ ~^ bit-wise XNOR & reduction AND | reduction OR ~& reduction NAND ~| reduction NOR ^ reduction XOR ~^ ^~ reduction XNOR << shift left >> shift right { } concatenation + - * / ** arithmetic % modulus > >= < <= relational! logical NOT && logical AND || logical OR == logical equality!= logical inequality === case equality!== case inequality? : conditional Used in comparing two variables (relational or logic 3:8 Decoder, Partially-Defined Output Cases; Example 5 •Example 5: Only 4 of the input combinations are defined: 000, 001, 100, 110 •Choose invalid inputs to have “x” output (trivial change e. Below is a list of all operators provided by Verilog and their precedence rules. Reduction Operators. Examples include >,+, ~, &,!=. v Declarations or concatena tion ari thmetic modulus relational logical negation logical and logical or logical equality logical inequality case equality case inequality bit-wise negation bit-wise and bit-wise inclusive or bit-wise exclusive or bit-wise equivalence reduction and reduction nand reduction or Combinatorial Verilog. or – takes the simulation specific number of bits or – takes the machine specific number of bits • If . The replication operator is used to replicate a group of bits n times. As one would expect, |, ^, ~&, and ~| reduction operators are available for OR, XOR, NAND, and NOR as well. They perform a bit-wise operation on a single operand to produce a single bit result. Reduction Verilog has six reduction operators, these operators accept a single vectored (multiple bit) operand, performs the appropriate bit-wise reduction on all bits of the operand, and returns a single bit result. radix. The structure of a module is the following: 2. 1800-2012 “System Verilog” – Unified hardware design, spec, verification • VHDL = VHSIC Hardware Description In Verilog we design modules, one of which will be identified as our top-level module. • Bitwise. MODEL N NMOS. In this case, the operation &x means x[3]&x[2]&x[ l]&x[O]. module and8(a, y); input [7:0] a; output y; assign y = &a; endmodule As one would expect, |, ^, ~&, and ~| reduction operators are available for OR, XOR, NAND, and NOR as well. Karthikeyan Sankaralingam Email (karu@cs. For reduction and, reduction or, and reduction xor operators, the first step of the operation shall apply the operator between the first bit of the operand and the second. There are two types of timing controls in Verilog - delay and event expressions. For example, the four bits of A are AND ed together to produce Y1. Shift Operators NAND Reduction : m && n: Logical AND |m: OR Reduction: m || n: Logical OR ~|m: NOR Reduction: m < n: Less Than ^m: XOR Reduction: m > n: Greater Than ~^m: NXOR Reduction: m <= n: Less Than or Equals: m == n: Equality: m >= n: Greater Than or Equals: m != n: Inequality: m === n: Identity: m !== n: Not Identical: m << const: Shift Left* m >> const: Shift Right* test ? m:n: Ternary {m, n} Concatenation {m{n}} Verilog Operators I Verilog contains operators that can be used to perform arithmetic, form logic expression, perform reductions/shifts, and check equality between signals. Verilog Operators. 6. Register and net (wire) operands are treated as unsigned. 5. reduction nand operator in verilog