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P7001: Difference between revisions
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added short description of firmware bug
(Added a little description of the A/D converters desgin flaw and some links to Tek magazines.) |
(added short description of firmware bug) |
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The A/D Converter uses a successive approximation technique to digitize the vertical and horizontal samples. The vertical resolution is 10 bits, the horizontal resolution 9 bits. It is worth mentioning that the vertical part of the signal is digitized in a range of 10 divisions. As a result, even signal components that are slightly above or below the screen edge are captured. A two bit memory location code (A, B, C or D) is added to the converted horizontal data. The result is the direct memory address at which the vertical data is stored to. For sweeps slower or equal to 500 μs/Div all 512 waveform points are digitized in one sweep. For faster sweep speeds the samples will be taken out-of-order with respect to their equivalent time in the waveform. In this case subsequent sweeps are needed complete the digitized data. The computer has direct access to the register of the A/D converter and may at any time read the last vertical sample. This makes it possible to create arrays with more than 512 elements. | The A/D Converter uses a successive approximation technique to digitize the vertical and horizontal samples. The vertical resolution is 10 bits, the horizontal resolution 9 bits. It is worth mentioning that the vertical part of the signal is digitized in a range of 10 divisions. As a result, even signal components that are slightly above or below the screen edge are captured. A two bit memory location code (A, B, C or D) is added to the converted horizontal data. The result is the direct memory address at which the vertical data is stored to. For sweeps slower or equal to 500 μs/Div all 512 waveform points are digitized in one sweep. For faster sweep speeds the samples will be taken out-of-order with respect to their equivalent time in the waveform. In this case subsequent sweeps are needed complete the digitized data. The computer has direct access to the register of the A/D converter and may at any time read the last vertical sample. This makes it possible to create arrays with more than 512 elements. | ||
===Hardware Signal Averager=== | ===Hardware Signal Averager=== | ||
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==Bugs & Errors== | |||
====Design Flaw of the A/D Converter==== | |||
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Tek_P7001_ADC_designflaw01.jpg | |||
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The dynamic range of the sampled waveform is greater than the converted output of the A/D converter. Any sampled point which is left to the crt viewing area will be added to memory location 0 and any point which is right to the crt viewing area will be added to memory location 511. The end points (0 and 511) of the acquired waveform data should be considered invalid for measurement purposes. [[Media:ServiceTekNotes 25 Sep 1982.pdf|ServiceTekNotes Issue 25, Sep 1982]] describes the problem and shows a possible solution. | |||
====Firmwarebug GPIB interface==== | |||
Affected Firmwareversion: at least 05/78 | |||
Due to an error in the firmware pin 9 of U123 is always configured as an output pin. This pin is directly connected to an output of the line driver IC U321. To prevent damage to the PIA chip it is recommended to remove the line driver U321. Since U321 is only needed for internal testing, it can be removed without any problem. | |||