verilog procedural assignment to a non register is not permitted

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  • module spi_master (
  • output [ 15 : 0 ] tx_data ,
  • input [ 15 : 0 ] rx_data ,
  • output mosi ,
  • input miso ,
  • output cs ,
  • output sck ,
  • input start
  • reg [ 15 : 0 ] tx_data ;
  • reg [ 3 : 0 ] tx_counter ;
  • reg [ 3 : 0 ] rx_counter ;
  • wire start ;
  • wire miso ;
  • initial begin
  • tx_counter [ 3 : 0 ] = 4 'b0;
  • rx_counter [3:0] = 4' b0 ;
  • always @( negedge sck ) begin
  • if ( cs == 0 && tx_counter != 4 'b1111) begin
  • #(5) mosi <= tx_data[tx_counter];
  • #(6) tx_counter <= tx_counter \+ 4' b1 ;
  • else if ( cs == 0 && tx_counter == 4 'b1111) begin
  • #(5) cs <= 1' b1 ;
  • else if ( cs == 1 && tx_counter == 0 ) begin
  • #(5) cs <= 1'b0;
  • always @( posedge sck ) begin
  • if ( cs == 0 && tx_counter <= 4 'b1111 && tx_counter >= 4' b0001 ) begin
  • #1 rx_data[rx_counter] <= miso;
  • #2 rx_counter <= rx_counter \+ 4'b1;
  • `include "spi_master.v"
  • module spi_master_tb(
  • reg [15:0] tx_data;
  • tx_data = 16'hF0AA;
  • #20 start = 1'b1;
  • #1000 $finish;
  • always begin
  • #1 clk = ~clk;
  • always @(start) begin
  • #10 sck = ~sck; // divided clk by CLK_DIVIDER
  • spi_master SPI_block(
  • reg [ 15 : 0 ] rx_data ;
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verilog procedural assignment to a non register is not permitted

gszakacs (Member)

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vivado报错:procedural assignment to a non-register result is not permitted“

verilog procedural assignment to a non register is not permitted

说明always语句内存在错误。可能原因为赋值语句有错误,或者程序块内信号有问题。

非阻塞逻辑:<= 阻塞逻辑:= 详细介绍见这位博主 总结: 1、时序逻辑一定用非阻塞赋值”<=”,一旦看到敏感列表有 posedge 就用”<=”。 2、组合逻辑一定用”=” ,一旦敏感列表没有 posedge 就用”=”,一旦看到 assign 就用”=”。 3、时序逻辑和组合逻辑分成不同的模块,即一个 always 模块里面只能出现非阻塞赋值”<=”或者”=”。 4、assign语句必须使用阻塞赋值

在assign内,被赋值的只能是reg类型的。而input output都是默认为wire类型。需要更改output类型的定义,例如由 output [2:0] d1 改为 output reg [2:0] d1

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verilog procedural assignment to a non register is not permitted

A procedural assignment updates the value of register data types.

Description:

Procedural assignments are used for updating register data types and memory data types.

The expression in a blocking procedural assignment is evaluated and assigned when the statement is encountered. In a begin-end sequential statement group, execution of the next statement is blocked until the assignment is complete.

In a non-blocking procedural assignment, the expression is evaluated when the statement is encountered, and assignment is postponed until the end of the time-step. In a begin-end sequential statement group, execution of the next statement is not blocked and may be evaluated before the assignment is complete. A group of statements with a non-blocking assignment has similar functionality as a group of statements within a fork-join block.

The left-hand side of a procedural assignment should be one of the following:

  • Register data type: reg , integer , time , real or realtime .
  • Bit-select of reg , integer or time .
  • Part-select of reg , integer or time .
  • Memory word.
  • Concatenation of any of the above.

When the right-hand side evaluates to a fewer bits than the left-hand side, the assignment to a reg does not sign-extend.

The evaluation of the assignment is delayed by the delay when the delay is specified before the register name. When the delay is specified before the expression, the expression is evaluated when the statement is encountered, and assigned in the time-step specified by the delay.

Continuous assignment , Expression , Net data type

  • Physical Design
  • Assertion Based Verification
  • Equivalence Checking
  • Simulation Based

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Verilog: Continuous & Procedural Assignments

verilog procedural assignment to a non register is not permitted

Continuous Assignment

Continuous assignment is used to drive a value on to a net in dataflow modeling. The net can be a vector or scalar, indexed part select, constant bit or part select of a vector. Concatenation is also supported with scalar vector types.

Regular & Implicit Assignment

Regular continuous assignment means, the declaration of a net and its continuous assignments are done in two different statements. But in implicit assignment, continuous assignment can be done on a net when it is declared itself. In the below example, `valid` is declared as wire during the assignment. If signal name is used to the left of the continuous assignment, an implicit net declaration will be inferred. In the below code `dout` is not declared as net, but it is inferred during assignment.

Procedural Assignment

We have already seen that continuous assignment updates net, but procedural assignment update values of reg, real, integer or time variable. The constant part select, indexed part select and bit select are possible for vector reg.

3 comments on “ Verilog: Continuous & Procedural Assignments ”

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Verilog Assignments

Variable declaration assignment, net declaration assignment, assign deassign, force release.

  • Procedural continuous

Legal LHS values

An assignment has two parts - right-hand side (RHS) and left-hand side (LHS) with an equal symbol (=) or a less than-equal symbol (<=) in between.

The RHS can contain any expression that evaluates to a final value while the LHS indicates a net or a variable to which the value in RHS is being assigned.

Procedural Assignment

Procedural assignments occur within procedures such as always , initial , task and functions and are used to place values onto variables. The variable will hold the value until the next assignment to the same variable.

The value will be placed onto the variable when the simulation executes this statement at some point during simulation time. This can be controlled and modified the way we want by the use of control flow statements such as if-else-if , case statement and looping mechanisms.

An initial value can be placed onto a variable at the time of its declaration as shown next. The assignment does not have a duration and holds the value until the next assignment to the same variable happens. Note that variable declaration assignments to an array are not allowed.

If the variable is initialized during declaration and at time 0 in an initial block as shown below, the order of evaluation is not guaranteed, and hence can have either 8'h05 or 8'hee.

Procedural blocks and assignments will be covered in more detail in a later section.

Continuous Assignment

This is used to assign values onto scalar and vector nets and happens whenever there is a change in the RHS. It provides a way to model combinational logic without specifying an interconnection of gates and makes it easier to drive the net with logical expressions.

Whenever b or c changes its value, then the whole expression in RHS will be evaluated and a will be updated with the new value.

This allows us to place a continuous assignment on the same statement that declares the net. Note that because a net can be declared only once, only one declaration assignment is possible for a net.

Procedural Continuous Assignment

  • assign ... deassign
  • force ... release

This will override all procedural assignments to a variable and is deactivated by using the same signal with deassign . The value of the variable will remain same until the variable gets a new value through a procedural or procedural continuous assignment. The LHS of an assign statement cannot be a bit-select, part-select or an array reference but can be a variable or a concatenation of variables.

These are similar to the assign - deassign statements but can also be applied to nets and variables. The LHS can be a bit-select of a net, part-select of a net, variable or a net but cannot be the reference to an array and bit/part select of a variable. The force statment will override all other assignments made to the variable until it is released using the release keyword.

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  3. Verilog: Prohibition of simultaneous assignment to a non-net

    verilog procedural assignment to a non register is not permitted

  4. Verilog代码题——基本电路_procedural assignment to a non-register data_out i-CSDN博客

    verilog procedural assignment to a non register is not permitted

  5. Verilog代码题——基本电路_procedural assignment to a non-register data_out i-CSDN博客

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VIDEO

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COMMENTS

  1. verilog

    3 Answers Sorted by: 12 There are more issues then then giving error message. As others have already pointed out result should be defined as output reg [63:0] result; The other issues will not generate a compiling error; they are generating incorrect behavior and are unsynthesizable. With the code:

  2. Procedural assignment to a non-register: assign vs always_comb?

    Procedural assignment to a non-register: assign vs always_comb? Vivado 2016.3, and SystemVerilog sources. Here's an SRAM controller for this asynchronous SRAM chip (the 10ns version). I'm using write cycle alternative 3 on page 15, which is where -OE is always held low.

  3. [Question] Procedural assignment to a non-register 'X' is not permitted

    December 28, 2015 at 4:45 PM [Question] Procedural assignment to a non-register 'X' is not permitted, left-hand side should be reg/integer/time/genvar Hi, I am a newbie at FPGA. Trying to write a SPI master module by myself to learn efficiently. Here is the spi_master module: module spi_master( output [15:0] tx_data, input [15:0] rx_data,

  4. Error: HDL Compiler : 1660 : Procedural assignment to a non-register

    You cannot do a procedural assignment (assignment inside an always statement or initial block) to a wire type as the error message has told you. Change the two outputs to output reg types if you wish to use them as the left hand side of a procedural assignment statement. Share Cite Follow answered May 7, 2020 at 11:06 Tom Carpenter 65.4k 3 145 202

  5. vivado报错:procedural assignment to a non-register result is not permitted"

    procedural assignment to a non -re gister F is not permitted "表示在代码的第31行,对一个非寄存器类型的信号F进行了过程赋值操作,这是不允许的。 3 3 根据引用 3 3 中的介绍,过程赋值使用的是非阻塞赋值"<= ",而非阻塞赋值只能用于时序逻辑中,对于组合逻辑应使用阻塞赋值"= "。

  6. Error: Verilog HDL Procedural Assignment error at <file

    Error: Verilog HDL Procedural Assignment error at <file... This error will occur in the Quartus® II software version 3.0 if you have made an illegal assignment to a signal that is not a reg data type. In the Verilog language, certain signal assignments can o

  7. Procedural assignment to a non-register is not permitted : r/FPGA

    Procedural assignment to a non-register 'note_group' is not permitted (for each row in the case statement and the one in the if rst statement.)

  8. verilog

    procedural assignment to a non-register i is not permitted

  9. Procedural Assignment

    Description: Procedural assignments are used for updating register data types and memory data types. The expression in a blocking procedural assignment is evaluated and assigned when the statement is encountered. In a begin-end sequential statement group, execution of the next statement is blocked until the assignment is complete. In a non ...

  10. Verilog: Continuous & Procedural Assignments

    There are two types of procedural assignments called blocking and non-blocking. Blocking assignment, as the name says, gets executed in the order statements are specified. The "=" is the symbol used for blocking assignment representation. Non-blocking assignment allows scheduling of assignments. It will not block the execution.

  11. Verilog Assignments

    This is used to assign values onto scalar and vector nets and happens whenever there is a change in the RHS. It provides a way to model combinational logic without specifying an interconnection of gates and makes it easier to drive the net with logical expressions. // Example model of an AND gate wire a, b, c; assign a = b & c; Whenever b or c ...

  12. Why does Xilinx throw this error? [Synth 8-2576] procedural assignment

    assign sw=LED; Something about this probably. Try doing sw <= LED; instead. The assign statement lives outside of your always blocks. Within those you want to only use nonblocking (<=) or blocking (=) operators. edit: What exactly are you trying to do?

  13. Synth 8-2576 procedural assignment to a non-register trig_i_a is not

    1 Answer Sorted by: 0 There are two problems here. Toolic is right that one of the problems is that you're trying to assign a value to an input and the error message isn't very helpful. But you're getting that error message because of a different problem the tool is noticing first.

  14. ASSIGNMENTS IN VERILOG

    Procedural assignments are used for updating register data types and memory data types. The expression in a blocking procedural assignment is evaluated and assigned when the statement is encountered.

  15. verilog

    1 Answer Sorted by: 0 In your code, output operand should be declared as reg, because in procedural block "always", you can not assign any value to a non-reg type. More informations here Share Improve this answer Follow edited Aug 22, 2019 at 9:27 barbsan 3,428 11 22 28

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    For example, such non-sale transfers would not involve a settlement agent or settlement statement or the transfer of funds through escrow. They may, however, involve an attorney or other real estate professional who prepares or files the deed, provides title insurance, or provides a title evaluation. 3. Designation Agreements

  17. help me solve concurrent assignment error in verilog for the code given

    However a wire cannot be assigned in a procedural code (ex always block). So you need to think how to assign some bits to from a module and other from procedural. \$\endgroup\$ - Greg

  18. verilog

    1 Answer Sorted by: 1 I get 3 syntax errors in your ex1 module. The trailing comma in a port list is illegal. Change: output wire c, to: output wire c It is illegal to assign a value to an input port inside a module. This is illegal: a=1'b1. Assuming it was a typo to use a there, and you really meant to type c, you should change: