Intel® Quartus® Prime Standard Edition User Guide: Debug Tools

Download PDF
ID 683552
Date 9/24/2018
Public
Document Table of Contents
Document Table of Contents x
1. System Debugging Tools Overview 2. Analyzing and Debugging Designs with System Console 3. Debugging Transceiver Links 4. Quick Design Debugging Using Signal Probe 5. Design Debugging with the Signal Tap Logic Analyzer 6. In-System Debugging Using External Logic Analyzers 7. In-System Modification of Memory and Constants 8. Design Debugging Using In-System Sources and Probes A. Intel® Quartus® Prime Standard Edition User Guides
1. System Debugging Tools Overview x
1.1. System Debugging Tools Portfolio 1.2. Tools for Monitoring RTL Nodes 1.3. Stimulus-Capable Tools 1.4. Virtual JTAG Interface Intel® FPGA IP 1.5. System-Level Debug Fabric 1.6. System Debugging Tools Overview Revision History
1.1. System Debugging Tools Portfolio x
1.1.1. System Debugging Tools Comparison 1.1.2. Suggested Tools for Common Debugging Requirements 1.1.3. Debugging Ecosystem
1.2. Tools for Monitoring RTL Nodes x
1.2.1. Resource Usage 1.2.2. Pin Usage 1.2.3. Usability Enhancements
1.2.1. Resource Usage x
1.2.1.1. Overhead Logic 1.2.1.2. Resource Estimation
1.2.2. Pin Usage x
1.2.2.1. For Signal Tap Logic Analyzer 1.2.2.2. For Signal Probe 1.2.2.3. For Logic Analyzer Interface
1.2.3. Usability Enhancements x
1.2.3.1. Incremental Compilation 1.2.3.2. Incremental Routing 1.2.3.3. Automation Via Scripting 1.2.3.4. Remote Debugging
1.3. Stimulus-Capable Tools x
1.3.1. In-System Sources and Probes 1.3.2. In-System Memory Content Editor 1.3.3. System Console
1.3.1. In-System Sources and Probes x
1.3.1.1. Push Button Functionality
1.3.2. In-System Memory Content Editor x
1.3.2.1. Generate Test Vectors
1.3.3. System Console x
1.3.3.1. Test Signal Integrity 1.3.3.2. Board Bring-Up and Verification 1.3.3.3. Test Link Signal Integrity with Transceiver Toolkit
2. Analyzing and Debugging Designs with System Console x
2.1. Introduction to System Console 2.2. System Console Debugging Flow 2.3. IP Cores that Interact with System Console 2.4. Starting System Console 2.5. System Console GUI 2.6. System Console Commands 2.7. Running System Console in Command-Line Mode 2.8. System Console Services 2.9. Working with Toolkits 2.10. ADC Toolkit 2.11. System Console Examples and Tutorials 2.12. On-Board Intel® FPGA Download Cable II Support 2.13. MATLAB* and Simulink* in a System Verification Flow 2.14. Deprecated Commands 2.15. Analyzing and Debugging Designs with the System Console Revision History
2.3. IP Cores that Interact with System Console x
2.3.1. Services Provided through Debug Agents
2.4. Starting System Console x
2.4.1. Starting System Console from Nios® II Command Shell 2.4.2. Starting Stand-Alone System Console 2.4.3. Starting System Console from Platform Designer (Standard) 2.4.4. Starting System Console from Intel® Quartus® Prime 2.4.5. Customizing Startup
2.5. System Console GUI x
2.5.1. System Explorer Pane
2.8. System Console Services x
2.8.1. Locating Available Services 2.8.2. Opening and Closing Services 2.8.3. SLD Service 2.8.4. In-System Sources and Probes Service 2.8.5. Monitor Service 2.8.6. Device Service 2.8.7. Design Service 2.8.8. Bytestream Service 2.8.9. JTAG Debug Service
2.8.3. SLD Service x
2.8.3.1. SLD Commands
2.8.4. In-System Sources and Probes Service x
2.8.4.1. In-System Sources and Probes Commands
2.8.5. Monitor Service x
2.8.5.1. Monitor Commands
2.8.6. Device Service x
2.8.6.1. Device Commands
2.8.7. Design Service x
2.8.7.1. Design Service Commands
2.8.8. Bytestream Service x
2.8.8.1. Bytestream Commands
2.8.9. JTAG Debug Service x
2.8.9.1. JTAG Debug Commands
2.9. Working with Toolkits x
2.9.1. Convert your Dashboard Scripts to Toolkit API 2.9.2. Creating a Toolkit Description File 2.9.3. Registering a Toolkit 2.9.4. Launching a Toolkit 2.9.5. Matching Toolkits with IP Cores 2.9.6. Toolkit API
2.9.6. Toolkit API x
2.9.6.1. Customizing Toolkit API Widgets 2.9.6.2. Toolkit API Script Examples 2.9.6.3. Toolkit API GUI Example 2.9.6.4. Toolkit API Commands 2.9.6.5. Toolkit API Properties
2.9.6.3. Toolkit API GUI Example x
2.9.6.3.1. Toolkit API GUI Example .tcl File
2.9.6.4. Toolkit API Commands x
2.9.6.4.1. toolkit_register 2.9.6.4.2. toolkit_open 2.9.6.4.3. get_quartus_ini 2.9.6.4.4. toolkit_get_context 2.9.6.4.5. toolkit_get_types 2.9.6.4.6. toolkit_get_properties 2.9.6.4.7. toolkit_add 2.9.6.4.8. toolkit_get_property 2.9.6.4.9. toolkit_set_property 2.9.6.4.10. toolkit_remove 2.9.6.4.11. toolkit_get_widget_dimensions
2.9.6.5. Toolkit API Properties x
2.9.6.5.1. Widget Types and Properties 2.9.6.5.2. barChart Properties 2.9.6.5.3. button Properties 2.9.6.5.4. checkBox Properties 2.9.6.5.5. comboBox Properties 2.9.6.5.6. dial Properties 2.9.6.5.7. fileChooserButton Properties 2.9.6.5.8. group Properties 2.9.6.5.9. label Properties 2.9.6.5.10. led Properties 2.9.6.5.11. lineChart Properties 2.9.6.5.12. list Properties 2.9.6.5.13. pieChart Properties 2.9.6.5.14. table Properties 2.9.6.5.15. text Properties 2.9.6.5.16. textField Properties 2.9.6.5.17. timeChart Properties 2.9.6.5.18. xyChart Properties
2.10. ADC Toolkit x
2.10.1. ADC Toolkit Terms 2.10.2. Setting the Frequency of the Reference Signal 2.10.3. Tuning the Signal Generator 2.10.4. Running a Signal Quality Test 2.10.5. Running a Linearity Test 2.10.6. ADC Toolkit Data Views
2.11. System Console Examples and Tutorials x
2.11.1. Nios® II Processor Example
2.11.1. Nios® II Processor Example x
2.11.1.1. Processor Commands
2.13. MATLAB* and Simulink* in a System Verification Flow x
2.13.1. Supported MATLAB* API Commands 2.13.2. High Level Flow
3. Debugging Transceiver Links x
3.1. Channel Manager 3.2. Transceiver Debugging Flow Walkthrough 3.3. Modifying the Design to Enable Transceiver Debug 3.4. Programming the Design into an Intel FPGA 3.5. Loading the Design in the Transceiver Toolkit 3.6. Linking Hardware Resources 3.7. Identifying Transceiver Channels 3.8. Creating Transceiver Links 3.9. Running Link Tests 3.10. Controlling PMA Analog Settings 3.11. User Interface Settings Reference 3.12. Troubleshooting Common Errors 3.13. Scripting API Reference 3.14. Debugging Transceiver Links Revision History
3.1. Channel Manager x
3.1.1. Channel Display Modes
3.3. Modifying the Design to Enable Transceiver Debug x
3.3.1. Adapting an Intel FPGA Design Example 3.3.2. Stratix® V Debug System Configuration 3.3.3. Instantiating and Parameterizing Intel® Arria® 10 Debug IP cores
3.3.1. Adapting an Intel FPGA Design Example x
3.3.1.1. Modifying Stratix® V Design Examples
3.3.1.1. Modifying Stratix® V Design Examples x
3.3.1.1.1. Generating reconfig_clk from an Internal PLL
3.3.2. Stratix® V Debug System Configuration x
3.3.2.1. Bit Error Rate Test Configuration ( Stratix® V) 3.3.2.2. PRBS Signal Eye Test Configuration ( Stratix® V) 3.3.2.3. Custom Traffic Signal Eye Test Configuration ( Stratix® V) 3.3.2.4. Link Optimization Test Configuration ( Stratix® V) 3.3.2.5. PMA Analog Setting Control Configuration ( Stratix® V)
3.3.3. Instantiating and Parameterizing Intel® Arria® 10 Debug IP cores x
3.3.3.1. Debug Settings for Transceiver IP Cores
3.6. Linking Hardware Resources x
3.6.1. Linking One Design to One Device 3.6.2. Linking Two Designs to Two Devices 3.6.3. Linking One Design on Two Devices 3.6.4. Linking Designs and Devices on Separate Boards 3.6.5. Verifying Hardware Connections
3.7. Identifying Transceiver Channels x
3.7.1. Controlling Transceiver Channels
3.9. Running Link Tests x
3.9.1. Running BER Tests 3.9.2. Signal Eye Margin Testing ( Stratix® V only) 3.9.3. Running Custom Traffic Tests ( Stratix® V only) 3.9.4. Link Optimization Tests
3.9.2. Signal Eye Margin Testing ( Stratix® V only) x
3.9.2.1. Running PRBS Signal Eye Tests ( Stratix® V only)
3.9.4. Link Optimization Tests x
3.9.4.1. Running the Auto Sweep Test 3.9.4.2. Determining the Best Tap Settings
3.10. Controlling PMA Analog Settings x
3.10.1. Intel® Arria® 10 and Intel® Cyclone® 10 GX PMA Settings
3.13. Scripting API Reference x
3.13.1. Transceiver Toolkit Commands 3.13.2. Data Pattern Generator Commands 3.13.3. Data Pattern Checker Commands
4. Quick Design Debugging Using Signal Probe x
4.1. Design Flow Using Signal Probe 4.2. Scripting Support 4.3. Quick Design Debugging Using Signal Probe Revision History
4.1. Design Flow Using Signal Probe x
4.1.1. Perform a Full Compilation 4.1.2. Reserve Signal Probe Pins 4.1.3. Assign Signal Probe Sources 4.1.4. Add Registers Between Pipeline Paths and Signal Probe Pins 4.1.5. Perform a Signal Probe Compilation 4.1.6. Analyze the Results of a Signal Probe Compilation 4.1.7. What a Signal Probe Compilation Does 4.1.8. Understanding the Results of a Signal Probe Compilation
4.1.8. Understanding the Results of a Signal Probe Compilation x
4.1.8.1. Analyzing Signal Probe Routing Failures
4.2. Scripting Support x
4.2.1. Making a Signal Probe Pin 4.2.2. Deleting a Signal Probe Pin 4.2.3. Enabling a Signal Probe Pin 4.2.4. Disabling a Signal Probe Pin 4.2.5. Performing a Signal Probe Compilation 4.2.6. Reserving Signal Probe Pins 4.2.7. Adding Signal Probe Sources 4.2.8. Assigning I/O Standards 4.2.9. Adding Registers for Pipelining 4.2.10. Running Signal Probe Immediately After a Full Compilation 4.2.11. Running Signal Probe Manually 4.2.12. Enabling or Disabling All Signal Probe Routing 4.2.13. Allowing Signal Probe to Modify Fitting Results
4.2.5. Performing a Signal Probe Compilation x
4.2.5.1. Script Example
4.2.6. Reserving Signal Probe Pins x
4.2.6.1. Common Problems When Reserving a Signal Probe Pin
5. Design Debugging with the Signal Tap Logic Analyzer x
5.1. The Signal Tap Logic Analyzer 5.2. Signal Tap Logic Analyzer Task Flow Overview 5.3. Configuring the Signal Tap Logic Analyzer 5.4. Defining Triggers 5.5. Compiling the Design 5.6. Program the Target Device or Devices 5.7. Running the Signal Tap Logic Analyzer 5.8. View, Analyze, and Use Captured Data 5.9. Other Features 5.10. Design Example: Using Signal Tap Logic Analyzers 5.11. Custom Triggering Flow Application Examples 5.12. Signal Tap Scripting Support 5.13. Design Debugging with the Signal Tap Logic Analyzer Revision History
5.1. The Signal Tap Logic Analyzer x
5.1.1. Hardware and Software Requirements 5.1.2. Signal Tap Logic Analyzer Features and Benefits 5.1.3. Backward Compatibility with Previous Versions of Intel® Quartus® Prime Software
5.1.1. Hardware and Software Requirements x
5.1.1.1. Opening the Standalone Signal Tap Logic Analyzer GUI
5.2. Signal Tap Logic Analyzer Task Flow Overview x
5.2.1. Add the Signal Tap Logic Analyzer to Your Design 5.2.2. Configure the Signal Tap Logic Analyzer 5.2.3. Define Trigger Conditions 5.2.4. Compile the Design 5.2.5. Program the Target Device or Devices 5.2.6. Run the Signal Tap Logic Analyzer 5.2.7. View, Analyze, and Use Captured Data
5.3. Configuring the Signal Tap Logic Analyzer x
5.3.1. Assigning an Acquisition Clock 5.3.2. Adding Signals to the Signal Tap File 5.3.3. Adding Signals with a Plug-In 5.3.4. Adding Finite State Machine State Encoding Registers 5.3.5. Specifying Sample Depth 5.3.6. Capture Data to a Specific RAM Type 5.3.7. Select the Buffer Acquisition Mode 5.3.8. Specifying Pipeline Settings 5.3.9. Filtering Relevant Samples 5.3.10. Manage Multiple Signal Tap Files and Configurations
5.3.2. Adding Signals to the Signal Tap File x
5.3.2.1. Pre-Synthesis Signals 5.3.2.2. Post-Fit Signals 5.3.2.3. Signal Preservation 5.3.2.4. Node List Signal Use Options 5.3.2.5. Signals Unavailable for Signal Tap Debugging
5.3.2.2. Post-Fit Signals x
5.3.2.2.1. Assigning Data Signals with the Technology Map Viewer
5.3.2.4. Node List Signal Use Options x
5.3.2.4.1. Disabling and Enabling a Signal Tap Instance
5.3.4. Adding Finite State Machine State Encoding Registers x
5.3.4.1. Modify and Restore Mnemonic Tables for State Machines 5.3.4.2. Additional Considerations for State Machines in Signal Tap
5.3.7. Select the Buffer Acquisition Mode x
5.3.7.1. Non-Segmented Buffer 5.3.7.2. Segmented Buffer
5.3.8. Specifying Pipeline Settings x
5.3.8.1. Specifying Pipeline Settings from Platform Designer (Standard)
5.3.9. Filtering Relevant Samples x
5.3.9.1. Input Port Mode 5.3.9.2. Transitional Mode 5.3.9.3. Conditional Mode 5.3.9.4. Start/Stop Mode 5.3.9.5. State-Based 5.3.9.6. Showing Data Discontinuities 5.3.9.7. Disable Storage Qualifier
5.3.10. Manage Multiple Signal Tap Files and Configurations x
5.3.10.1. Data Log Pane 5.3.10.2. SOF Manager
5.4. Defining Triggers x
5.4.1. Basic Trigger Conditions 5.4.2. Comparison Trigger Conditions 5.4.3. Advanced Trigger Conditions 5.4.4. Custom Trigger HDL Object 5.4.5. Trigger Condition Flow Control 5.4.6. Specify Trigger Position 5.4.7. Power-Up Triggers 5.4.8. External Triggers
5.4.1. Basic Trigger Conditions x
5.4.1.1. Using the Basic OR Trigger Condition with Nested Groups
5.4.2. Comparison Trigger Conditions x
5.4.2.1. Specifying the Comparison Trigger Conditions
5.4.3. Advanced Trigger Conditions x
5.4.3.1. Examples of Advanced Triggering Expressions
5.4.4. Custom Trigger HDL Object x
5.4.4.1. Using the Custom Trigger HDL Object 5.4.4.2. Required Inputs and Outputs of Custom Trigger HDL Module 5.4.4.3. Custom Trigger HDL Module Properties
5.4.5. Trigger Condition Flow Control x
5.4.5.1. Sequential Triggering 5.4.5.2. State-Based Triggering 5.4.5.3. Signal Tap Trigger Flow Description Language 5.4.5.4. State-Based Storage Qualifier Feature
5.4.5.1. Sequential Triggering x
5.4.5.1.1. Configuring the Sequential Triggering Flow 5.4.5.1.2. Trigger that Skips Clock Cycles after Hitting Condition 5.4.5.1.3. Storage Qualification with Post-Fill Count Value Less than m
5.4.5.2. State-Based Triggering x
5.4.5.2.1. State-Based Triggering Flow Tab 5.4.5.2.2. Trigger Lock Mode
5.4.5.3. Signal Tap Trigger Flow Description Language x
5.4.5.3.1. <state_label> 5.4.5.3.2. <boolean_expression> 5.4.5.3.3. <action_list>
5.4.5.4. State-Based Storage Qualifier Feature x
5.4.5.4.1. Storage Qualification Feature for the State-Based Trigger Flow.
5.4.6. Specify Trigger Position x
5.4.6.1. Post-fill Count
5.4.7. Power-Up Triggers x
5.4.7.1. Enabling a Power-Up Trigger 5.4.7.2. Configuring Power-Up Trigger Conditions 5.4.7.3. Managing Signal Tap Instances with Run-Time and Power-Up Trigger Conditions
5.4.8. External Triggers x
5.4.8.1. Using the Trigger Out of One Analyzer as the Trigger In of Another Analyzer
5.5. Compiling the Design x
5.5.1. Faster Compilations with Intel® Quartus® Prime Incremental Compilation 5.5.2. Prevent Changes Requiring Recompilation 5.5.3. Verify Whether You Need to Recompile Your Project 5.5.4. Incremental Route with Rapid Recompile 5.5.5. Timing Preservation with the Signal Tap Logic Analyzer 5.5.6. Performance and Resource Considerations
5.5.1. Faster Compilations with Intel® Quartus® Prime Incremental Compilation x
5.5.1.1. Enabling Incremental Compilation for Your Design 5.5.1.2. Using Incremental Compilation with the Signal Tap Logic Analyzer
5.5.4. Incremental Route with Rapid Recompile x
5.5.4.1. Using the Incremental Route Flow 5.5.4.2. Tips to Achieve Maximum Speedup
5.5.6. Performance and Resource Considerations x
5.5.6.1. Signal Tap Logic in Critical Path 5.5.6.2. Signal Tap Logic Using Critical Resources
5.6. Program the Target Device or Devices x
5.6.1. Ensure Setting Compatibility Between .stp and .sof Files
5.7. Running the Signal Tap Logic Analyzer x
5.7.1. Runtime Reconfigurable Options 5.7.2. Signal Tap Status Messages
5.8. View, Analyze, and Use Captured Data x
5.8.1. Capturing Data Using Segmented Buffers 5.8.2. Differences in Pre-Fill Write Behavior Between Different Acquisition Modes 5.8.3. Creating Mnemonics for Bit Patterns 5.8.4. Automatic Mnemonics with a Plug-In 5.8.5. Locating a Node in the Design 5.8.6. Saving Captured Data 5.8.7. Exporting Captured Data to Other File Formats 5.8.8. Creating a Signal Tap List File
5.8.2. Differences in Pre-Fill Write Behavior Between Different Acquisition Modes x
5.8.2.1. Example
5.9. Other Features x
5.9.1. Creating Signal Tap File from Design Instances 5.9.2. Using the Signal Tap MATLAB* MEX Function to Capture Data 5.9.3. Using Signal Tap in a Lab Environment 5.9.4. Remote Debugging Using the Signal Tap Logic Analyzer 5.9.5. Using the Signal Tap Logic Analyzer in Devices with Configuration Bitstream Security 5.9.6. Monitor FPGA Resources Used by the Signal Tap Logic Analyzer
5.9.1. Creating Signal Tap File from Design Instances x
5.9.1.1. Creating a .stp File from a Design Instance
5.9.4. Remote Debugging Using the Signal Tap Logic Analyzer x
5.9.4.1. Debugging Using a Local PC and an SoC 5.9.4.2. Debugging Using a Local PC and a Remote PC
5.9.4.2. Debugging Using a Local PC and a Remote PC x
5.9.4.2.1. Equipment Setup
5.11. Custom Triggering Flow Application Examples x
5.11.1. Design Example 1: Specifying a Custom Trigger Position 5.11.2. Design Example 2: Trigger When triggercond1 Occurs Ten Times between triggercond2 and triggercond3
5.12. Signal Tap Scripting Support x
5.12.1. Signal Tap Command-Line Options 5.12.2. Data Capture from the Command Line
6. In-System Debugging Using External Logic Analyzers x
6.1. About the Intel® Quartus® Prime Logic Analyzer Interface 6.2. Choosing a Logic Analyzer 6.3. Flow for Using the LAI 6.4. Controlling the Active Bank During Runtime 6.5. Using the LAI with Incremental Compilation 6.6. LAI Core Parameters 6.7. In-System Debugging Using External Logic Analyzers Revision History
6.2. Choosing a Logic Analyzer x
6.2.1. Required Components
6.3. Flow for Using the LAI x
6.3.1. Defining Parameters for the Logic Analyzer Interface 6.3.2. Mapping the LAI File Pins to Available I/O Pins 6.3.3. Mapping Internal Signals to the LAI Banks 6.3.4. Compiling Your Intel® Quartus® Prime Project 6.3.5. Programming Your Intel-Supported Device Using the LAI
6.4. Controlling the Active Bank During Runtime x
6.4.1. Acquiring Data on Your Logic Analyzer
7. In-System Modification of Memory and Constants x
7.1. Setting Up In-System Modifiable Memories and Constants 7.2. Running the In-System Memory Content Editor 7.3. In-System Modification of Memory and Constants Revision History
7.2. Running the In-System Memory Content Editor x
7.2.1. Instance Manager 7.2.2. Editing Data Displayed in the Hex Editor Pane 7.2.3. Importing and Exporting Memory Files 7.2.4. Scripting Support 7.2.5. Programming the Device with the In-System Memory Content Editor 7.2.6. Example: Using the In-System Memory Content Editor with the Signal Tap Logic Analyzer
8. Design Debugging Using In-System Sources and Probes x
8.1. Hardware and Software Requirements 8.2. Design Flow Using the In-System Sources and Probes Editor 8.3. Compiling the Design 8.4. Running the In-System Sources and Probes Editor 8.5. Tcl interface for the In-System Sources and Probes Editor 8.6. Design Example: Dynamic PLL Reconfiguration 8.7. Design Debugging Using In-System Sources and Probes Revision History
8.2. Design Flow Using the In-System Sources and Probes Editor x
8.2.1. Instantiating the In-System Sources and Probes IP Core 8.2.2. In-System Sources and Probes IP Core Parameters
8.4. Running the In-System Sources and Probes Editor x
8.4.1. In-System Sources and Probes Editor GUI 8.4.2. Programming Your Device With JTAG Chain Configuration 8.4.3. Instance Manager 8.4.4. In-System Sources and Probes Editor Pane
8.4.4. In-System Sources and Probes Editor Pane x
8.4.4.1. Reading Probe Data 8.4.4.2. Writing Data 8.4.4.3. Organizing Data
1. System Debugging Tools Overview
2. Analyzing and Debugging Designs with System Console
3. Debugging Transceiver Links
4. Quick Design Debugging Using Signal Probe
5. Design Debugging with the Signal Tap Logic Analyzer
6. In-System Debugging Using External Logic Analyzers
7. In-System Modification of Memory and Constants
8. Design Debugging Using In-System Sources and Probes
A. Intel® Quartus® Prime Standard Edition User Guides

2.8.9.1. JTAG Debug Commands

JTAG Debug commands help debug the JTAG Chain connected to a device.

Table 12.  JTAG Debug Commands
Command Argument Function
jtag_debug_loop <service-path> <list_of_byte_values> Loops the specified list of bytes through a loopback of tdi and tdo of a system-level debug (SLD) node. Returns the list of byte values in the order that they were received. This command blocks until all bytes are received. Byte values have the 0x (hexadecimal) prefix and are delineated by spaces.
jtag_debug_sample_clock <service-path> Returns the clock signal of the system clock that drives the module's system interface. The clock value is sampled asynchronously; consequently, you must sample the clock several times to guarantee that it is switching.
jtag_debug_sample_reset <service-path> Returns the value of the reset_n signal of the Avalon® -ST JTAG Interface core. If reset_n is low (asserted), the value is 0 and if reset_n is high (deasserted), the value is 1.
jtag_debug_sense_clock <service-path> Returns a sticky bit that monitors system clock activity. If the clock switched at least once since the last execution of this command, returns 1. Otherwise, returns 0.. The sticky bit is reset to 0 on read.
jtag_debug_reset_system <service-path> Issues a reset request to the specified service. Connectivity within your device determines which part of the system is reset.
Level Two Title