Questions tagged [testbench]

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SystemVerilog ring oscillator simulation with different delays

I am currently encountering issues with my ring oscillator simulation in SystemVerilog, which I cannot explain. Toolchain: ...
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1 answer
43 views

SystemVerilog - clk not toggling in verification

I'm testing an AES encryption machine that's written in Verilog. I know that the DUT is perfect because I created a Verilog testbench. When I simulate in VCS, the clk stays at 0 the whole time and the ...
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1 answer
139 views

Is it possible to access signals in a DUT from a testbench written in a different HDL?

I believe such a question has been asked in the past but this is more comprehensive. VHDL provides "external name" where we use an alias in a testbench to access signals that exist down the ...
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1 answer
83 views

MAX134 and MAX3001E Troubleshooting

This is going to be a long question because I plan to include a lot of context that I feel is important to grasp the full scope of my issue. I am currently a senior year university student hard at ...
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1 answer
34 views

Test/programming rig with spring-loaded probes/connectors

I have ESP32-CAM module with two rows of 0.1" male pins. The pins are 0.22" high. Here is a picture: I would like to trim them, so they are too short to mate with the corresponding female ...
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1 vote
1 answer
111 views

Resources for learning Open Source VHDL Verification Methodology (OSVVM) [closed]

I am looking forward to learn Open Source VHDL Verification Methodology (OSVVM). In this regard, I wanted to know the following: Can I use Xilinx ISE v10.1 and its in-built simulator for OSVVM based ...
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1 vote
1 answer
82 views

Signals acting weirdly in VHDL

I've always been told that a signal updates its values after a wait statement, or after a rising edge if we have for example if rising_edge(clk) then but in this testbench, after the first wait ...
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1 answer
60 views

8bitworkshop(verilog) to terminal transition

I have been working through very basic Verilog code examples at https://8bitworkshop.com (supports a book I am following). I understand there are a few good online options available and will pursue ...
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1 answer
167 views

Delays and/or how to manually cycle clock in a loop when building Verilog testbench to test FSM for microcode/ROM conversion

I am working on a project wherein I need to convert a Finite State Machine coded in Verilog into a ROM. In order to do this I need to create a memory file for the ROM version of the FSM which stores ...
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1 answer
240 views

Verilog Simulation: 16 to 1 Mux Output High Z

Verilog beginner here. I am attempting to implement a 16to1 mux by instantiating four 4to1 muxes. Here is my code: .v file: ...
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Clock network remains at x when applying fast clock frequencies

I am required to test how a design behaves if it is run with extremely fast clock frequencies (higher than the maximum frequency allowed by timing constraints). The goal is to detect what kind of ...
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Why does this file give me "syntax error: I give up." in verilog program?

This is my original file saved as "example.v" module example(a,b,y); input b,y; output a; assign a=b&y; endmodule This is my testbench file ...
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55 views

Off the Shelf Current Sensors?

What are the tradeoffs between making my own current sense setup with a precision shunt resistor and ADC versus just buying something? What are the most popular COTS current sensors for shunt current ...
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2 answers
133 views

Verilog Code test bench problem

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2 votes
1 answer
100 views

Model running slower than RTL in SystemVerilog

I'm testing an RTL implementation of a certain block from a 3rd party company in SystemVerilog using Questa. The block is fairly large and my block which acts as a wrapper around it is also large. The ...
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1 answer
37 views

Unexpected behaviour of data memory in modelsim testbench

I am describing a very simple ram memory in VHDL and observing strange behaviour which I do not understand nor am able to debug. I have similar code written elsewhere and I suspect that rewriting it ...
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1 answer
109 views

Why does my VHDL simulation fail after one input for this device?

EDIT: Found a solution. See the bottom of the post I am wondering why my simulation of the following entity fails to run for more than one input. When I change the inputs, the system crashes, and I ...
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1 vote
1 answer
56 views

How can I make Verilog HDL ModelSim test bench for a simple ripple adder circuit output an addition table instead of a long list of every calculation?

I've completed my assignment and I'd like to make the output look something like this, with one table for sum output and one table for carry output: ...
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108 views

Can I use a bench power supply as a substitute for a 9V DC adapter?

I want to test a guitar pedal but I don’t have a 9V adapter around - but I do have access to a DC power supply. Is it possible* to alligator clip the +ve to the power terminal and ground to the ...
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1 answer
105 views

Test bench when design is pipelined

I have a design with chained modules. Each of them is a pipelined design, so the output in each of them take more than 1 clock cycle. To perform the test bench, I have created so many registered ...
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2 answers
1k views

Why do we declare the inputs of our design as reg in testbench and outputs as wire?

Why do we declare the inputs of our design as reg in testbench and outputs as wire?
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1 vote
2 answers
82 views

Testbench using Task operation [closed]

I have to write a testbench using "tasks" to verify the functionality of an 8-bit ALU. My tasks are not getting simulated properly in EDA playground. Can anyone please tell me where my ...
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1 vote
2 answers
228 views

How more efficiently can I write the test bench for a MOD 16 asynchronous counter using JK flip flop?

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2 votes
2 answers
103 views

Creating a three phase current system with e.g. 70Hz instead of 50Hz

I am doing magnetic field measurements on a 3-phase cable dummy, in order to develope a distance measurement system for power cables. This is a uni research project. For a test setup I want to create ...
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1 vote
0 answers
114 views

TTL in an RF switch

I am hoping to find help on how to properly connect supply voltage to my switch assembly in order to actuate. My switch has input requirement of +15, -15, GND, and +5V. Also, the 5v logic inputs. ...
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3 votes
1 answer
489 views

VHDL Clock Divider Problem

I have a 100 Mhz clock and I need a 0.5 Khz clock. So I wrote this code: ...
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1 vote
2 answers
526 views

How can I improve my testbench for testing a 1024x4 RAM memory in Verilog

This is a question following on from my previous one "How can I improve my testbench for testing a 1024x4 RAM memory in Verilog". Basically, I have modified the previous solution in an ...
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0 answers
253 views

ModelSim does not run until "$stop" command after editing my testbench

I keep running into this issue where my code stops running before the "@stop" command. This only occurs whenever I add code in Libero and then go back to ModelSim. When I go to simulate in ...
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1 vote
1 answer
124 views

What can I do to improve my test bench for testing a 64x4 RAM memory in Verilog

What can I do to improve my test bench for testing a 64x4 RAM memory in Verilog to obtain the desired result? I have written a test bench to test a simple 64x4 RAM memory in Verilog and it seems to &...
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  • 511
-2 votes
1 answer
61 views

Not getting correct results displayed from register

I am trying to input the numbers 1,0,3,2,32'hFFFFFFFF,32'h00000001 into the registers 0,1,2,3,6, and 7 respectively. I am doing this through always @(posedge clk) ...
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2 answers
228 views

Can I feed my level shifter with a voltage divider?

I need to level shift 3V3 to 2V8. I have a 2V8 source but that'll require some patching wires on testpads and as such I would like to avoid it. I'm wondering: would it be safe to feed the SN74LVC245AN ...
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3 votes
1 answer
397 views

Pass parameters to covergroups in SV Testbench

I am trying to create a parameterized covergroup in my testbench as follows: ...
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0 votes
1 answer
473 views

Syntax error near "else" in Verilog, in an initial block, next to assert

I'm trying to make a self-checking testbench for an ALU I'm designing for an extra credit assignment. Here's what I have: ...
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-1 votes
2 answers
90 views

Test Verilog FSM for state with no reset

My professor gave us several Verilog test files to write Verilog test benches for. In the test bench, we're supposed to initialize the state to 0, apply random inputs, and check to see if we have ...
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1 vote
1 answer
157 views

How do I implement the clock into this testbench?

I am trying to write a testbench for an adder/subtractor but when it compiles the clock does not shift. Here is the verilog for the adder/subtractor: ...
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0 votes
1 answer
178 views

VHDL test bench for input port assignment

I am trying to depict port 3 of microcontroller which acts a I/O and as special functions like timers interrupts in VHDL. The code is as follows: ...
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1 vote
2 answers
80 views

How to efficiently mux many signals to/from a climate chamber?

I am building a setup to measure various parameters across a temperature range from -55°C to +125°C. The devices under test will be placed in a climate chamber. There are around 10 signals from each ...
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1 vote
0 answers
334 views

Using an internal signal in a testbench

I am using HDL Designer and have a pretty large design I need to test. I have created a test bench by using HDL Designer itself and did not do it standalone. Like the title states, I want to know how ...
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0 votes
1 answer
92 views

Two questions about testing with HDL designer

I hope it's okay to ask about specific programs here. I have successfully created a test bench with HDL designer, and I use Modelsim to simulate. By pressing the Modelsim icon and selecting "through ...
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1 vote
2 answers
5k views

Verilog Testbench - wait for specific number of clock cycle edges

In my testbench, I want to wait for two events in sequence: one after 60000 clock cycles and next after additional 5000 clock cycles I know I can wait for clock edges using statement @(posedge clk), ...
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2 answers
195 views

Ultracapacitor initial voltage drop during discharging

I've been building a test stand for ultracapacitors, with very simple schematic looking like this: simulate this circuit – Schematic created using CircuitLab The resistor on the bottom is to ...
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7 votes
3 answers
3k views

VHDL: What is correct way to model open collector output for FPGA?

I2C uses open collector outputs. FPGAs do not have such outputs. They do have tri state buffers though. How should open collector output be defined in a VHDL for an FPGA? How should open collector ...
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1 vote
0 answers
494 views

VHDL - rand*real(2**32-1) : can this cause an overflow issue?

I'm studying VHDL implementations of multipliers: I found this one and i'm trying to modify it. Default word size is 8 bit and the design is working (both simulation and synthesis) for any size up to ...
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0 votes
1 answer
1k views

Variable frequency for sine wave in Verilog [duplicate]

I am trying to implement 4 different frequencies at which sine wave is going to be simulated in testbench. I am using a counter to do so. However, it can not toggle clk_out in simulation window. Not ...
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2 votes
2 answers
241 views

Xilinx's ISE (GSR): The initial block adds a delay of 100 time units to simulation

I'm working on a lab assignment in which I'm supposed to simulate a sequential logic circuit (A ROM device). I'm using xilinx's ISE as IDE. My implementation works fine and the logic and the data is ...
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0 votes
1 answer
1k views

Unable to diagnose StX fault in Modelsim

I'm unable to figure out why Modelsim is giving me a StX fault for this testbench. I'm just creating a counter and simulating a device that returns the MSB of the counter. Any help in figuring out ...
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0 votes
1 answer
3k views

VHDL: reading integers from a text file, storing them in array, and writing in text format again

In a certain simulation testbench using questasim, I am trying to read the files with integers numbers which looks like, ...
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-1 votes
1 answer
990 views

Understanding Testbench Waveform for UART module

I have taken the following code for testing a UART module from https://www.nandland.com/vhdl/modules/module-uart-serial-port-rs232.html Can anyone explain what is happening in the ...
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0 votes
1 answer
339 views

VHDL Output is Unitiliazed or Zero when simulated

I am new to VHDL and implementing a test bench. I am trying to write code for a simple 2:1 MUX where the output of the MUX enters an active high synchronous LOAD register. Inputs and outputs are 8 ...
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1 answer
2k views

How do I override generic values in a VHDL testbench?

I am new to VHDL, and I'm working with an off-the-shelf UART block. I'm trying to create a test bench and override the data width, but I get errors saying that my signals are undeclared: ERROR - C:/...
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