Logic Analyzer

Logic Analyzer

Varsha Karambelkar MTech Student

Department of Electronics Engg, Bharati Vidyapeeth Deemed University, Pune, Maharashtra, India. 411 043

Prof. A.A.Shinde Department of Electronics Engg,

Bharati Vidyapeeth Deemed University, Pune, Maharashtra, India. 411 043

Abstract

Due to the fast development of electronic devices, the digital circuit designing takes up more and more percentage in total electronic developments thus in the process of debugging and doing validation in a digital system, one of the common task a designer need to do is the acquisition of digital waveforms. The waveforms can be captured by the device Logic Analyzer.

As digital circuit is too fast to be observed by a human being, the basic idea to capture waveforms at higher speed is to implement the design using ARM controller which internally uses RISC Machine unlik e simple processors. ARM based embedded systems, providing a low-cost solution to meet the request of flexibility and testability

Logic analyzer is a dedicated application The main objective is to use module as powerful Lab equipment to check and verify the design under test (digital circuit) for design and verification engineers with smaller size and less expensive.

Keywords: Logic analyzer, ARM, RISC

1. Introduction

   In order to deliver correct-the-first-time products with co mple x system require ments and time-to-market pressure design verification is vital in the embedded system design process. A possible choice for verification is to simulate the system being designed.

   If a high-level mode l for the system is used, simu lation is fast but may not be accurate enough, with a low-level model too much time may be required to achieve the desired level of confidence in the quality of the evaluation. Since debugging of real systems has to take into account the behaviour of the target system as well as its environ ment, runtime in formation is e xtre me ly impo rtant.

   Along with the designing of any digital system it is also necessary to debug and validate the system For debugging the system, different tests are needed to perform on digital waveforms[1]. Log ic Analyzer is a tool that allows numerous digital waveforms to be acquired simu ltaneously. To acquire different dig ital waveforms a Logic Analyzer is a multi-channel device. The ma jor function of an oscilloscope is to display the analogue characteristics, voltage scope and the spurious interference of a signal.

   The logic analyzer is designed for digital circuit s because of inherence of a signal, it works on the aspects of voltage level. Each channel inputs one digital signal.

   It is the aim that in near future this system will gain the same popularity as a DMM of present time.

   When we connect an analyzer to a digital c ircu it, we are on ly concerned with the logic state of the signal. It measures and analyzes signals differently than an oscilloscope. It doesn't measure analog details. Instead, it detects logic threshold levels. The advantages of Logic analyze r over oscilloscope are it can monitor mu lt iple channel at a t ime w ith good and various triggers .It can be used as a powerful analysis function [3]. For testing a digital circu it using analyzer, only log ic state of the signal is considered. The digital systems are faster compared to analog systems so acquiring the data will require higher rate and acquisition of data with high speed is possible with A RM machine as RISC machines are faster.[1]

   The acquisition can be clocked internally, or the test system can provide the sample clock. It is designed to trigger a complicated sequence of digital events, and then copy a large a mount of dig ital data fro m the system under test. The captured data will enable the user to locate failure of the digita l system. The acquisition channel is connected to the System Under Test through test probe. The input voltage is compared against the threshold voltage and decision about the signal's logic state (1or 0) is made.[2] The Logic Analy zer uses the PC as its displaying platfo rm and communicates with the devices through USB ports. It also supports the most popular Windows system and provides convenient User Interface. With its powerful triggering abilities user can easily find out even slightest errors within the system. Logic Analyzer is used to debug and verify digital system operation, used to detect and analyze timing violations and transients on buses and to trace embedded software e xecution [3]

2. System Architecture

A logic analy zer is an electronic instru ment which displays signals of a dig ital c ircu it. A logic analyze r may convert the captured data into timing diagrams, protocol decodes, state machine traces, assembly language, or correlate assembly with source-level software. Logic Analy zer is a mu lti-channel device which helps in d isplaying the digital waveforms.

With the rapid development of the field of industrial process control and the fast popularization of embedded ARM processor, it has been a trend that ARM processor can substitute the single-chip to

realize data acquisition and control. Proposed system is based on embedded ARM processor (LPC2148)

The module inc ludes different parts -The first part includes different testing digital circuit like timer, flip flop, counter Time r can be used to generate a square waveform of part icular frequency or variable frequency or it can be diffe rent mic rocontroller signals

As embedded systems are getting more comple x, the need for thorough testing becomes increasingly important.

Advances in surface-mount packaging and multip le- layer PCB fabricat ion have resulted in smaller boards and more compact layout, making traditional test methods, e.g., e xte rnal test probes and "bed-of-nails" test fixtures, harder to imple ment. As a result, acquiring signals on boards, can be beneficia l to hardware testing and software development, It a lso include the probe to be connected from testing circuit to ARM board

The second part includes actual ARM board to capture real t ime signals of d igital c ircuits The ARM 7TDMI-S is a general purpose 32-bit microprocessor, which offe rs high performance and very low power consumption. The ARM architecture is based on Reduced Instruction Set Co mputer (RISC) princ iples, and the instruction set and related decode mechanism are much simpler than those of mic ro progra mmed Co mple x Instruction Set Co mputers (CISC). This simplic ity results in a high instruction throughput and impressive real-time interrupt response from a sma ll and cost-effective processor core. Pipeline techniques are employed so that all parts of the processing and me mory systems can operate continuously. Typically, while one instruction is being e xecuted, its successor is being decoded, and a third instruction is being fetched from me mory.

The advantage of using RISC processor is that the processor use smalle r die sizes and requires shorter time to develop. The processors gives higher performance than CISC. It uses high clock rate with single cycle The ARM board is connected to PC through USB connector The further part includes displaying the captured waveforms on the PC with the help of GUI control signals. The waveforms can be saved on the PC and retrieved back to analy ze or to debug the different timing signals

The GUI (Graphica l User Interface) inc ludes diffe rent control buttons to connect different serial ports, hardware testing, debugging i.e capturing as data logging and analyzing i.e loading timing signals which are saved in data logging window

Allow input from keyboard, read and send on COM port for testing

Is TEST mode

or CAPTURE

mode

TEST

Capture

START

Initialize COM port for sending data

Initialize ARM controller with SFR

3 .Block Diagram 4.Flow Chart

Connect the circuit to be tested to ARM kit through probes

Capture the values from test circuit, save in the memory

Send the captured data on selected COM port to PC via USB

Repeat the process of capturing & saving sending values to PC. Display the values in wave format

In LOAD mode, signals are verified with expected output of test circuits

1. Applications

   Laborator y Pur pos e

   Oscillator measure ment: Observe the waveforms to find out if there are burrs or interfe res or if change in frequency

   Ti ming me asurements Measure the timing of signals to find out conflicts or timing proble ms

   Assistance on analysis It provides additional analysis to bus signals or protocol to simp lify the development cycle.

   Bug finder ; Logic ana lyze r can be used for error tracing or finding erro r bugs.

   Multichannel Me asuring: It has 8 channels it can handle this kind of measure ment easily.

   Bus Fre quenc y me asure ment Trigger ability

   Err or Captures

2. Conclusion

The successful completion of the nodule can be used as low cost powerful lab equip ment to debug and verify diffe rent digital systems with like timers, counters ,microcontrolle r c ircu its

REFERENCES

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   Source:

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[17]

http://www.linkinstruments.com/logic%20analyzer%20softwar e.htm