[introduction]What the word of time relation logarithm between signal designs is reliable move crucial. To synchronous design, clock signal photograph is attached most importance to especially to the time of data signal should. Use mixture signal oscilloscope, can decide many logic are inputted and the time between clock signal concerns easily. Build and maintain time trigger to decide clock and data time concern automatically.

What the word of time relation logarithm between signal designs is reliable move crucial. To synchronous design, clock signal photograph is attached most importance to especially to the time of data signal should. Use mixture signal oscilloscope, can decide many logic are inputted and the time between clock signal concerns easily. Build and maintain time trigger to decide clock and data time concern automatically.

Set-up time is to point to before effective clock brim happens, data-in signal keeps stable (tall or low) time. Holding time is to point to after effective clock brim happens, data-in signal keeps stable (tall or low) time. Synchronous parts of an apparatus (like trigger) set in component data manual install and hold time. Must satisfy setting and the requirement that hold time, ability ensures element can work reliably correctly.

Mixture signal oscillograph (MSO) because can be caught,with time associated format shows them, the signal integrality that suits signal of number of test and verify very much and debug digital circuit. The article is a specification with 5 series MSO, 2, 4, 5 with mode of operation of 6 series MSO identical. MSO2000 and MSO5000 series oscillograph follow same principle, but user interface differs somewhat. They combined the basic function of the function of professional class oscillograph and logistic analyzer. Oscillograph of mixture region of 3 series MDO, MDO3000 and MDO4000 series also provides function of analyzer of 16 passageways logic. Here, any functions that mention in MSO or ability also apply to MDO product.

MSO setting

Resolution of time of manage skill word (digital sampling is led)

An important MSO collects norms is to be used at capturing the time resolution of digital signal. Sampling rate differs somewhat between different MSO type. When undertaking time is measured build and maintenance, it is very important that understanding time measures resolution.

Digital sampling rate and record length

Watch 1 listed build and maintain time norms of integrated circuit, be second of a few accept normally or shorter. When the digital logic input that should use MSO checks them, must consider the time resolution of logistic input.

Graph 1. Use measure extent of signal of logic of fast test and verify automatically.

Set digital threshold value

The digital passageway of mixture signal oscillograph resembles digital circuit same, regard digital signal as logic tall or logic is low. This is meant as long as too ringing, strong play with the ground do not cause logistic changeover, these imitate character are not a problem to MSO. Like logistic analyzer, it is logistic that MSO uses the threshold value voltage that the user appoints to decide signal be being returned high is logistic low.

The imitate passageway of MSO can check the logistic amplitude of digital signal quickly. In the graph 1 in, oscillograph measures the extent of digital signal automatically to be 3.6V about. To having the logistic series of semmetry voltage amplitude, be like CMOS, threshold value is the half of signal extent. However, asymmetrical to having the logistic series of voltage amplitude, be like TTL (transistor – transistor is logistic) , the biggest low n that normally need consults package data is expressed and is threshold value definition logistic parts of an apparatus inputs voltage (TTLVIL=0.8V) input voltage with the smallest tall n (TTLVIH=2.0V) the midpoint between (=1.4V of TTLV threshold value) .

Graph 2. In same the setting on probe group mixes a TLP058 number logic logistic series (TTL and CMOS) threshold value.

Most peaceful overcomes MSO to provide setting of every passageway threshold value, this is very useful to debugging the circuit that has mixture logic series. Graph 2 showed 5 series MSO uses probe of 8 passageways TLP058 to measure many logistic signal. Setting of TTL signal threshold value is 1.7V, setting of 3.3VCMOS signal threshold value is 1.65V, setting of 5VCMOS signal threshold value is 2.5V, can collect all sorts of logistic signal reliably at the same time thereby.

To 3 series MDO, MSO2000 and MDO3000 series, threshold value is to press probe group (the group of a 8 passageways) adjust, because this TTL signal will be on group of a probe, and LVPECL signal will be on group of the 2nd probe.

Graph 3. Probe colour coding and photograph of undee colour coding match, make see which test nods which signal correspondence more easily.

Unscramble color to code digital weaveform shows

The number is time weaveform and imitate weaveform are very similar, show logic is mixed high only low n. Analyse to simplify, tektronixMDO/MSO oscillograph shows logistic low n for blue, logistic tall n shows for green, although transfer sightless, also can see logistic value. The color of undee label still matchs with the colour coding photograph of probe, make see which test nods which signal correspondence more easily, if pursue,3 are shown.

Graph 4. What go up in MDO/MSO series is time collect give typical examples. Defined 3 collateral bus line, the clock signal that uses parts of an apparatus undertakes decipher to its.

The number times weaveform can set a bus line. Signal of a number is by the definition lowest is effective, what other figure signal is worth on behalf of the binary system is other, till highest and effective. Next, oscillograph is bus line decipher binary system or hexadecimal value.

Graph 5. Imitate passageway and digital channel time are right neat.

Eliminate the time deflection between the passageway

Every Tektronix MDO or MSO series oscillograph have compatible logistic probe. To simplify the number is measured, oscillograph can compensate the transmission defer of logistic probe. Accordingly, do not need those who have digital passageway probe to differ corrective.

However, to undertake the time correlation between imitate and digital weaveform is measured better, important is to eliminate imitate to arrive time deflection of the number. It is in the give a demonstration that the graph shows 5 times, to be opposite imitate passageway and digital passageway neat, the 2V of imitate weaveform (50% extent) the position and the digital signal bridging time that happen in place of 2V threshold value are right neat. The hand is moved adjust differ the value arrives together with be opposite imitate passageway digital passageway. This differs corrective process need repeats to any other imitate passageways undertake.

Should change when imitate probe, should check the deflection of imitate passageway; When measuring different logistic set, should check digital threshold value. After configuring good threshold value and deflection, oscillograph can be used at test and verify to mix debug digital circuit.

Graph 7. This 74HCT74 trigger is pressed it seems that expect the job.

Graph 6. Trigger behavior give typical examples.

Trigger time is measured

The simplest synchronous and logistic parts of an apparatus is trigger. The logistic condition that D inputs is only after clock ascendant edge (after transmitting defer through D trigger) just can appear on Q output. MSO is status of job of trigger of test and verify and the ideal tool that debug digital circuit.

At first sight, if the graph is shown 7 times, trigger is pressed it seems that expect the job. Data signal had stabilized second of a few accept before clock ascendant edge, and maintain after clock edge stabilized second of a few accept. The transmission defer that outputs to Q from clock edge is 6 accept second about.

Graph 8. The set-up time on 74HCT74 trigger is violated compasses bring about Q output to was not changed.

In the graph 8 in, data signal is before clock edge only 300ps happening changes, far the set-up time under 15ns is normative — this is a set-up time is violated compasses. Attention, q is outputted if anticipate,did not change position in that way.

The attention pursues 8 in signal transfers the gray area all round. MSO shows these area to lead relevant time uncertainty in order to indicate with digital sampling.

Graph 9. The maintenance on 74HCT74 trigger time is violated compasses bring about Q output to was not changed.

Graph 9 showed signal of a data is after clock edge about the example that 300ps happening changes. This is far under the maintenance of 3ns time is normative — this is one maintains time to violate compasses. Notice again, q is outputted if anticipate,did not change position in that way.

Graph 10. Be built automatically and maintain time on 74LVCG74 trigger to violate compasses spark captured a lot of mistakes.

Capture build and maintain time to violate compasses

MSO has a kind to spark technically mode, aim to capture automatically every are built and / or maintain time to violate compasses. Build and maintain time trigger to measure clock signal and data signal (or the data signal on certain MSO) the time between concerns, be in set-up time or hold time under capture when the standard signal. This kind of function simplified to debug the job, the unmanned value that still can be used at the design defends monitoring.

Consulting after 74LVCG74 component data is expressed, will be built and maintain time to spark parameter is installed respectively for 2 accept second and 1 accept second, in order to capture any violating compasses circumstance, if pursue,10 are shown. MSO can spark automatically the input condition that appoints parameter is disobeyed to go up in the first.

Graph 11. Pulse width trigger captures on the output of 74LS74 trigger narrow pulse breakdown.

In an example, build and maintain trigger to be used at sparking the input of trigger. Another kind of method is to spark the signal that equipment outputs is wrong, capture input signal undertakes an analysis.

In next case, one is based on 74LS74 low power comsumption the old design of technology of TTL of Xiao Te radical appeared intermittence mistake. The lowest of tall n outputs voltage to be 2.4V, because this all tall n is outputted,signal should achieve this voltage at least. This design is based on 20MHz clock (periodic 50ns) , because this is all,the width of output pulse should obtain this periodic in part at least.

After mastering these information, oscillograph can output signal to whether be pressed certainly quickly expect the job, be in abnormal when capture input and output signal. Graph 11 a when showed pulse width trigger captures narrow pulse breakdown, namely the half of the width of the smallest pulse that pulse width is less than this design to anticipate.

Graph 12. Narrow pulse trigger captured easily the low range on 74LS74 trigger output is narrow pulse.

It is not just intermittence breakdown appeared on the output in trigger, a few breakdown still show low extent. Graph 12 showed narrow the low extent pulse that pulse trigger captures, these pulse do not accord with the standard of package.

Graph 13. The set-up time on 74LVCG74 trigger is violated compasses the cursor that spark is measured.

Use these sparking to install medium any, you can capture input and output signal. Graph the 13 set-up time that showed use cursor undertakes are measured, indicated set-up time clearly to violate compasses (about 6ns, far the least value under 20ns) . Mixture signal oscillograph combined the imitate signal of basic logistic analyzer function and oscillograph to analyse a function.

Tektronix MSO and MDO series include to build and maintain time to spark, pulse sparks and sampling of high resolution number, in order to facilitate fast number is debugged.

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