List of

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Figures

NXScope NXscope capture process

NXscope generator Generator GUI

file name

NXBoard NXboard GUI

NXBoard NXboard GUI scope menu

example 1 functional block diagram

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display caused by an erroneous sample

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NXscope Overview

NXscope is an embedded logic analyser. It enables analyzer enabling you to sample a collection of internal data synchronously with a user’s clock (rising edge sensitive) and analyse the sampled record samples of your design’s internal signals at the rising clock edge and analyze the results in a waveform viewer.

•  NXscope is implements a NanoXplore IP Core . It is generated by using the NXcore generatorGenerator

• The capture process is controlled by JTAG via through the ANGIE USB-JTAG adapter with commands supported by via NXbase2 software or the NXboard GUI

• The results can be are displayed and analysed analyzed with either of the following toostools:

  • The ModelSim Waveform Viewer (, using a simple simplified testbench to read the .txt TXT file generated by the NXcore generator and display the waveforms)

  • The GTKWave Waveform Viewer (free waveform display toolsoftware)

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The NXscope IP Core is made of 3main comprises 3 main functional blocks:

• The Trigger Engine
  A configurable module for detecting the trigger conditions to launch the capture samples capture

• The Capture Unit
  This A configurable module stores to store the captured samples according to trigger conditions

• The JTAG Interface
  Enablesthe Activates the trigger engine to start and reads the transfers captured samples to send them via the workstation through the ANGIE USB-JTAG adapter to the computer using via NXbase2 software or the NXboard GUI

NXscope Features

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Trigger Features

• 1 to 32 trigger input lines

• Optional trig_immediate input

• Single or dual sequential trigger conditions

• Level-based (basic) or level- and edges-based (basic_and_edges) triggertriggers

Capture

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Settings

• Capture width: 2 to 240 input lines

• Capture depth: 2K, 4K, 6K, 8K, 12K, 24K or 48K

• Programmable number of samples stored before trigger condition

• Optional windowed capture by windows mode (the capture depth is sub-divided in multiple sub- windows)

• Optionally stores the TRIG_PULSEtrigger pulse

• Optionally stores the Window number, if applicable

NXscope trigger and capture conditions are flexible:

• Up to 32 trigger lines

• Single or two-level trigger conditions

• Basic trigger conditions on ‘0’, ‘1’ or ‘X’ on each one of the trigger lines

• Edge detection (rising, falling or both) on up to 32 trigger lines

• User’s defined pre-trigger storage (not available when two-level trigger is selected)

• Trig on condition(s)

• Trig immediate (no condition)

• Up to 240 sampled signals

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Using NXscope is typically a four 4-step process which consists of:

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describes in the sections below.

Step 1: Generate the NXscope IP Core

The NXscope IP Core is generated by using the NXcore generator tool. It can then be instantiated in the user’s designAll trigger using the NXcore Generator tool.

All triggers and data sampling parameters are defined by the user . This includesincluding:

• Number of data lines to be sampled (up to 240)

• Sampling depth

• Trigger conditions

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o   Post or pre-trigger storage: The user can specify the number of samples to be stored before the trigger condition has been met.

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Next generation versions will provide higher flexibility and more advanced features.

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Step 2: Instantiate the Generated NXscope IP Core in your

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Design

After generating its your customized NXscope IP Core, the user you must instantiate it in its design, and launch the implementation and bitstream generationyour Design.

The Input and Output signals to be connected are as follows:

Inputs

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Name	Type	Description
CLK : in	std_logic;	User’s clockUser Clock
ENA : in	std_logic;	Enables the clock edges for all NXscope internal logic, including trigger and capture. Can be tied to ‘1’ if not required.used
TRIG_LINES : in	std_logic_vector	User’s User-defined (1 to 32 bits-bit)
DATA_LINES : in	std_logic_vector	User’s User-defined (2 to 240 bits-bit)
TRIG_IMMEDIATE : in	std_logic;	Can be optionally used to resume a pending capture when the trigger condition can’t be met. Starts an immediate capture when going high.

 

Outputs

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JTAG Pins

The captured samples are read by “nxbase2” NXbase2 or “nxboard” NXboard software , via the ANGIE USB-JTAG adapter.

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Step 3: Implement the Design and Generate the Bitstream

1. Synthesise, Place and Route your design and generate

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1. your Bitstream using Impulse or nxpython as described in the Impulse Design Flow manual

2. Check the reports to ensure timing constraints are met

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Step 4: Launch NXbase2/NXboard and NXscope

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Commands

Using NXbase2 software or NXboard GUI.

See chapter 3 for basic instructions referring to NXbase2 and/or NXboard commands.

For the NXboard interface, follow these steps:

1. Load your Bitstream

2. Start the sample capture

3. Retrieve the captured data

See the NxBase2 User Manual for more detailed information about the available NXscope commands please refer to the NXbase2 user’s manual.

Once the data has been captured, an ACSII ASCII file is generated (.in TXT or .VCD), and the results can be analyzed VCD format.

You can review the TXT results via a simple testbench in the ModelSim waveform viewer (.TXT result file), with a simple testbench or with the free GTKwave waveform display software using the .VCD result file.

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or the VCD results using the free open-source GTKwave waveform viewing software.

Create a Custom NXscope IP Core

The NXscope generator is a GUI where you can Generator interface enables you to define all available parameters of the logic analyzer.

In order to To launch the NXscope generatorGenerator, launch first the NXcore GUI (by typing the “nxcore” “NXcore” command at the prompt, and then, select the “NXscope” icon on the GUI left top side.

The next figure is a screen capture of the NXcore / NXscope generator Generator GUI. All customizable parameters are available in this single page.  Anchor_Figure2_Figure2on this single page.

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When all NXscope parameters are set, the IP Core can be generated by pressing the « generate » command, in the bottom-right part of the window.

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Entity Name

The NXscope generator Generator generates a VHDL encrypted file. The entity name is entered here. The VHDL path and file name are chosen with the “Generate” (bottom-right of the window).

The entity can then be instantiated in the design as a VHDL component.

The generated VHDL file includes a header (not encrypted) where the user can see the ports port names, modes, and width.

Capture

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Configuration Input line count: integer range 2 to 240

Up to 240 internal signals can be sampled and captured.

 Capture_depth: integer range 2048 to 49152

Defines the capture depth of the DATA_LINES sampled and stored on internal RAM block(s). The maximum depth is 48K.

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Both “Capture_depth” and “Input line count” define the amount of internal RAM to be used by the IP Core, as for example:

• A single memory block can store up to 2048 x 24-bit words.

• With 10 RAM blocks up to 24K x 20-bit words can be stored.

 Capture_mode: “Pre-trigger” or “Multiple windows”

This setting allows enables you to assign one or more capture windows to the NXscope capture memory.

• “Pre-trigger”: the “Capture depth” is used as a single capture windows window that uses the whole depth. In this mode, the user can define the number of samples to be stored before reaching the trigger condition. For example, a 2048-word allows to enables you store N samples before, and 2048-N samples after the trigger condition. Alternately, this mode supports a two-level trigger. In this case, a first trigger condition must be met, then the second (and final) trigger condition starts the data capture.

• “Multiple windows”: the “Capture depth” is divided in into multiple sub-windows allowing multiple captures until filling the complete available RAM. As an example, if “Capture depth” = 2K, the user can define 4 windows of 512 samples. The setting of “Window capture length” defines the length of the sub-windows.

 Window capture length: integer range 64 to 2048

This  setting  allows  to  define setting enables you to define  the length of  the the  capture  windows  when when  “Capture mode” = “Multiple windows”.

 Pre-trigger_

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samples: integer range 0 to capture_depth-1

• When “Capture mode” is set to “Pre-trigger” and “Multiple level trigger” is “false” it’s possible to sample data before reaching the trigger condition. “Pre-trigger samples” defines the number of samples acquired before the trigger condition is met.

• If “Multiple level trigger” is set to true, the value of “Pre-trigger samples” is ignored, and the capture starts when the second trigger condition is met.

However, in any mode, the user has still the option to store up to 2 samples to be acquired before triggering, by using the “User data delay” setting.

 User data delay: integer range 0 to 2

Available in all trigger modes, this setting allows to store storage of 0 to 2 samples before meeting the trigger condition. It can be particularly useful in “Multiple windows” mode, or “Pre-trigger” if “Multiple level trigger” is set to true. It allows to capture and visualize up to 2 samples before the trigger condition is met.

Note that this option requires using additional logic resources for implementation.

 Store trigger pulse: Enable or Disable

This setting allows enables you to store the trigger pulse (when the trigger condition is met), so it can appear automatically as an additional additionally captured data_line.

When “Store trigger pulse” = “Enable”, the number of sampled signals is then:

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The user’s defined sampled bits being Input line count -1 downto 0, so the weight (index) of the trigger pulse in the captured flow is “Input line count”.

 Store window number: Enable or Disable

When “Capture mode” is set to “Multiple windows”, the total capture depth is split in into several capture windows. The length of each window is defined with the “Window capture length” parameter.

NXscope gives the user the ability to store the window number for each partial capture. This option can be helpful for the visualization and identification of the several capture sets.

When “Store window number” is set to “Enable”, four additional bits are stored in the capture memory, giving up to 16 different windows window numbers (can be helpful to clearly identify each capture window when displaying the resulting waveform. The number of signals sampled by NXscope will be:

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o   “Input line count” + 5 if “Store trigger pulse” = 1”. In this case, the windows window number are stored as:

(“Input line count” + 4 downto “Input line count” + 1).

Trigger

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Configuration

Trigger line count: integer range 1 to 32

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Trigger mode: “Basic” or “Basic & Edges”

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There are two possible 2 trigger modes:

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Multiple level trigger: “Enable” or “Disable”

When “Capture mode” is set to “Pre-trigger” the user can define a two-level trigger condition. The analyzer will search first for the first level trigger condition, before searching for the second level and final trigger condition and start the data capture. For this, the “Multiple level trigger” must be set to true, and the “First level trigger value” must be defined by the user.

The NXscope IP Core output goes from a low state to high when the first trigger condition has been met. 

Trigger

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Value

When “Trigger mode” is set to “Basic”, each trigger line will be compared to the following possible values: ‘0’, ‘1’ or ‘Ignore’

When “Trigger mode” is set to “Basic & Edges”, each trigger line will be compared to the following possible values: ‘0’, ‘1’, ‘Rising edge’, Falling Edge’, ‘Both Edges’ or ‘Ignore’

First level trigger value:

When”Multiple ” Multiple level trigger” is set to “Enable”, the pre-trigger condition must be specified too.

If this option is disabledisabled, the “First level trigger value” is ignored.

NXscope IP Core

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Generation:

Once the NXscope parameters are set, press the “Generate” command icon in the bottom-right part of the window.

A new window appears. It allows you to choose both file name and path.

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A VHDL encrypted file is then generated. A header in clear VHDL (not encrypted) is available. This header appears as comments. It can be used for the component declaration when instantiating the NXscope IP Core in the design to be analyzed.

NXscope

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Capture Tools

After compiling the design, the user must send the bitstream to the FPGA and then launch the data capture.

The user You can launch the capture in two different ways :

With nxbase2 software:

Loading using NXbase2 or NXboard as described in the sections below.

Launch Sample Capture with NXbase2

Use NXbase2_cli to run the following commands:

1. Load the bitstream:

   Code Block
   >>

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1. NXbase2_cli

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1. –s /bitstream_path/bitstream_name.nxb

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1. Launch a capture*:

   • For a (ModelSIM) TXT file

     Code Block
     >>

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1. • NXscope capture dump.txt 50E6

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1. • For (GTKWave) VCD file

     Code Block
     >>

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1. • NXscope capture dump.vcd 50E6

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*Where 50E6 is the estimated frequency of the sample frequency clock for this example the design (50 * 10**6 = 50 MHz in this case).

The frequency value doesn’t have any does not impact on the acquisition. It’s just used for the generation of the It is used to generate the VCD file , if this format is chosen. 

If required, the user can chose the path to save the captured results.

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Launch Sample Capture with NXboard

At the prompt, launch the following command:

>>nxboard>>NXboard

NXboard GUI appears:

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Note that the value given to the “Capture Frequency” is taken in into account only for the VCD file generation if this format is chosen.

A message will be issued after the captured data has been stored in the specified file.

NXscope results format:

NXscope can store the captured results in two possible formats:

• .txt: preferred format for waveform display on ModelSim/QuestaSim

• .vcd: preferred format for waveform display on GTKwave – free software

NXscope

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Capture Sequence

After configuring the FPGA with the bitstream containing the NXscope IP Core and before launching the NXscope capture command, the “DONE” and ‘TRIG_ARMED” output pins of the NXscope IP Core are low. The IP Core is waiting for a command.

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After filling the assigned internal RAM the capture stops and the “DONE” output goes high. At this time, the NXboard / NXbase2 software starts reading the captured data via the ANGIE USB-JTAG adapter. A message appears on the console to inform that reading is complete.

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In order to To prevent such a situation, it’s possible to use the optional input pin of the NXscope IP Core “TRIGGER_IMMEDIATE”. This pin must be tied to a low state in a normal situation. When it goes high, an immediate acquisition is started, ignoring the trigger condition(s).

NXscope capture and display example

Launch

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NXbase2/NXboard and NXscope commands

In order to To sample the data lines, you must use the Angie USB-JTAG adapter, and the NXbase2 software or NXboard GUI.

The bitstream must first be first loaded , then before the capture can be launched as specified in the previous chaptersection.

For detailed information about the available commands please refer to the NXbase2 NxBase2 user’s manual.

Once the data has been captured, an ACSII file is generated (.TXT or .VCD). The results can be then analyzed in the ModelSim waveform viewer (.TXT result file), with a simple testbench or with the free GTKWave waveform display software using the .VCD result file.

Display and analysis of the captured results

Open ModelSim and launch the testbench simulation

As mentioned previously the ModelSim waveform viewer can be used to visualize and analyze the captured results (.TXT result file).

The. TXT file generated with the sampled results is read by a simple testbench, to be converted to graphic waveforms.

Have a look on See the following example:

library ieee;

use ieee.std_logic_1164.ALL;

library STD;

use STD.textio.all;

use ieee.std_logic_textio.all;

 

entity TB_NXscope is

end TB_NXscope;

 

architecture TB_ARCHI of TB_NXscope is

 

signal CLK        : std_logic;

signal SAMPLES: std_logic_vector(25+1 downto 0);

 

signal DIN : std_logic_vector(10 downto 0);

signal DIN_VALID  : std_logic;

signal DOUT : std_logic_vector(11 downto 0);

signal DOUT_VALID : std_logic;

 

signal TRIG_PLS   : std_logic;

begin

 

process

file RESULT       : text;

variable LINE_VAR : line;

variable DVAR : std_logic_vector(25+1 downto 0);

begin

   file_open(RESULT, "dump.txt", read_mode);

   while not(endfile(RESULT))  loop

      wait until rising_edge(CLK);

      readline(RESULT, LINE_VAR);

      read(LINE_VAR, DVAR);

      SAMPLES <= DVAR;

   end loop;

   file_close(RESULT);

   wait;

end process;

process  begin

   CLK <= '0';  wait for 10 ns;

   CLK <= '1';  wait for 10 ns;

end process; 

 

DIN        <= SAMPLES(10 downto 0);

DIN_VALID  <= SAMPLES(11);

DOUT       <= SAMPLES(23 downto 12);

DOUT_VALID <= SAMPLES(24);

 

TRIG_PLS   <= SAMPLES(25);

 

end TB_ARCHI;

The user can then set its own waveform settings.

Open the .VCD result file with GTKWave and view/analyze the captured results

GTKWave is a free waveform display software. It allows enables you to display the waveform of signals that are stored in .VCD format.

Please, refer to the GTKWave documentation for detailed information.

NXscope IP Core configuration examples

The following shows three different examples of NXscope configurations.

Example 1: 12K x (25 + 1) capture with 50 samples pre-trigger condition

Number_of_trig_lines = 4

Input line count = 25

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Functional block diagram

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Example 2: 24K x (33 + 1) capture (2 samples pre-trig cond)

Number_of_trig_lines = 6

Input line count = 33

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Functional block diagram

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5.3    Example 3: 8K x (42 + 1 + 4) capture (2 samples pre-trig cond)

Number_of_trig_lines = 8

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Functional block diagram

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6 Known issues

Erroneous single sample in the captured stream:

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This sample can appear anywhere in the waveform. FortunatellyFortunately, it’s easy to recognize, and it must be ignored.

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NanoXplore is working to correct this problem as soon as possible.

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7 How to order a NXscope license

NXscope license is not included in the “”nxmap” “nxmap” software. A separate license must be ordered.

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