In the Tektronix 2467 oscilloscope manual there is a TTL/CMOS logic measurement that I don't understand how they are using it. Can you guys please read this and see how they use this feature to troubleshoot logic TTL/CMOS circuits.
Observing Coincidence of Digital Signals
With digital signals applied to CH 1 and CH 2, the Add waveform is high when both signals are high, low when both are low, and at an intermediate level when one signal is high and the other is low. By inverting CH 2, you can observe the coincidence of one signal and NOT the other. To observe coincidence of TTL signals:
1. Connect the signals of interest to CH 1 and CH 2. If the coincidence of interest has one signal high and the other one low, invert CH 2.
2. Display CH 1, CH 2, and Add. Set both VOLTS/DIV to 2 V and both inputs to GND. Position both channels on screen and the Add trace one division above the bottom of the graticule. Then deselect CH 1 and CH 2.
3. Set both inputs to DC. Set Trigger mode to Auto and Source to Vert. If the coincidence of interest is high-high, set trigger SLOPE to -t-. If the coincidence is low-low, set SLOPE to - . (If CH 2 is inverted, consider the inverse of the CH 2 signal in the high-high or low-low combination.) Press INIT@50%, then carefully adjust the trigger level to respond to the high-high or Low-low state combination. (Trigger level readout doesn't operate with Add Source.)
4. Now you can observe and measure coincidence durations and other time intervals. Channels 3 and 4 can show relationships to other signals.
Observing Coincidence of Digital Signals
With digital signals applied to CH 1 and CH 2, the Add waveform is high when both signals are high, low when both are low, and at an intermediate level when one signal is high and the other is low. By inverting CH 2, you can observe the coincidence of one signal and NOT the other. To observe coincidence of TTL signals:
1. Connect the signals of interest to CH 1 and CH 2. If the coincidence of interest has one signal high and the other one low, invert CH 2.
2. Display CH 1, CH 2, and Add. Set both VOLTS/DIV to 2 V and both inputs to GND. Position both channels on screen and the Add trace one division above the bottom of the graticule. Then deselect CH 1 and CH 2.
3. Set both inputs to DC. Set Trigger mode to Auto and Source to Vert. If the coincidence of interest is high-high, set trigger SLOPE to -t-. If the coincidence is low-low, set SLOPE to - . (If CH 2 is inverted, consider the inverse of the CH 2 signal in the high-high or low-low combination.) Press INIT@50%, then carefully adjust the trigger level to respond to the high-high or Low-low state combination. (Trigger level readout doesn't operate with Add Source.)
4. Now you can observe and measure coincidence durations and other time intervals. Channels 3 and 4 can show relationships to other signals.
