Kenwood CS-1352 Instruction Manual

waveform. In this case, the output waveform isshifted with respect to the leading edge of thereference frequency pulse by a time interval cor-responding to the pulse width.Divide-by-8 Circuit Waveforms:Fig. 6 indicates waveform relationships for a basicdivide-by-eight circuit. The oscilloscope settingsare identical to those used in F i g . 5. Thereference frequency of Fig. 6A is supplied to theChannel 1 input. Fig. 6B indicates the ideal timerelationship between the input pulses and the out-put pulse.In an application where the logic circuitry isoperating at or near its maximum design frequency,the accumulated rise time effects of the con-secutive stages produce a built-in time propagationdelay which can be significant in a critical circuitand must be compensated for. Fig. 6 C indicatesthe possible time delay which may be introducedinto a frequency divider circuit. By use of the dual-trace oscilloscope, the input and output waveformscan be superimposed (ADD or S U B ) to determinethe exact amount of propagation delay that occurs.A . R E F E R E N C E F R E Q U E N C Y P U L S E T R A I N( 1 0 0 0 P U L S E S P E R S E C O N D )B. I D E A L D I V I D E B Y E I G H T O U T P U TPropagation Delay Time Measurement:A n example of propagation dealy in a divide-by-eight circuit w a s given in the previous paragraph.Significant propagation delay may occur in any cir-cuit. This oscilloscope has features which simplifymeasurement of propagation delay. Fig. 7 showsthe resultant waveforms when the dual-tracepresentation is combined into a single-tracepresentation by selecting the A D D or S U B (CH2P O L A R I T Y P U L L INV) position of the M O D Eswitch. In the A D D position the two inputs arealgebraically added in a single-trace display.Similarly, in the INV. (pull) position the two inputsare algebraically subtracted. Either positionprovides a precise display of the propagation time(Tp). Using the procedure given for calibrated timemeasurement ( C A L ) , Tp can be measured. A more10precise measurement can be measured. A moreprecise measurement can be obtained if the Tp por-tion of the waveform is expanded horizontally. Thismay be done by pulling the X 5 M A G control. Italso may be possible to view the desired portion ofthe waveform at a faster sweep speed.E X P A N D T H I S P O R T I O NF O R T I M E M O R E P R E C I S EM E A S U R E M E N TDigital Circuit Time Delay Measurement:Since a dual-trace oscilloscope has the capability ofcomparing the timing of one waveform withanother, it is necessity in designing, manufacturingand servicing digital equipment. In digital equip-ment, it is common for a larger number of circuitsto be synchronized, or to have a specific time-relationship to end other. Many of the circuits arefrequency dividers a s previously described, butwaveforms are often time-related in many othercombinations. In the dynamic state, some of thewaveforms change depending upon the input ormore of operation. Fig. 8 shows a typical digitalcuicuit and identifies several of the points at whichwaveform measurements are appropriate. The a c -companying Fig. 9 shows the normal waveforms tobe expected at each of these points and their tim-ing relationship. The individual waveforms havelimited value unless their timing relationship to oneor more of the other waveforms is known to be cor-rect. The dual-trace oscilloscope allows this com-parison to be made. In typical fashion, waveformNo. 3 would be displayed on Channel 1 andC . P R O P A G A T I O N D E L A Y IN D I V I D E B YE I G H T C I R C U I TFig. 6 Waveforms in divide-by-eight circuitFig. 7 Using A D D or S U B modes forpropagation time measurementC H 1C H 2A D DS U B