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7854: Difference between revisions
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{{Spec | Memory capacity | 2048 waveform points in up to 16 waveforms (optional expansion to 5120 points and 40 waveforms) }} | {{Spec | Memory capacity | 2048 waveform points in up to 16 waveforms (optional expansion to 5120 points and 40 waveforms) }} | ||
{{Spec | Single shot | events and pretrigger up to 50 µs/div ("2.5 µs/point") with the [[7B87]] Time Base}} | {{Spec | Single shot | events and pretrigger up to 50 µs/div ("2.5 µs/point") with the [[7B87]] Time Base}} | ||
{{Spec | CRT | [[154-0644-05]] ([[Phosphor| | {{Spec | CRT | [[154-0644-05]] ([[Phosphor|P31]]) or [[154-0893-09]] ([[Phosphor|P11]]); cathode −3 kV, anode +21 kV, [[distributed deflection plates|distributed vertical deflection plates]] }} | ||
{{Spec | Features | | {{Spec | Features | | ||
* Signal | * Signal averaging | ||
* Cursor measurements | * Cursor measurements | ||
* Waveform parameter measurements | * Waveform parameter measurements | ||
* GPIB | * GPIB interface (standard) | ||
* Waveform calculation operators - add, multiply, square root, log, abs | * Waveform calculation operators - add, multiply, square root, log, abs | ||
* Internal RPN programming language (Reverse Polish Notation) | * Internal RPN programming language (Reverse Polish Notation) | ||
* Keystroke | * Keystroke programming (up to 2000 keystrokes with option 2D) | ||
* | * Programmable text display on screen | ||
}} | }} | ||
{{EndSpecs}} | {{EndSpecs}} | ||
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==Internals== | ==Internals== | ||
The acquisition system uses what Tektronix termed a "display-oriented random sampling digitizing technique". | The acquisition system uses what Tektronix termed a "display-oriented random sampling digitizing technique". | ||
It simultaneously digitizes a pair of X and Y signal values at a rate of 3.5 µs/point, using Schottky diode bridge based sample/hold circuits and a single 10-bit successive-approximation ADC. | It simultaneously digitizes a pair of X and Y signal values at a rate of 3.5 µs/point, using Schottky diode bridge based sample/hold circuits and a single 10-bit successive-approximation ADC. | ||
The Y sample value is then written into the memory location addressed by the X value, using DMA. | The Y sample value is then written into the memory location addressed by the X value, using DMA. | ||
The CPU in the 7854 is a [ | The CPU in the 7854 is a [[Texas Instruments TMS9900]] 16-bit microprocessor, known from the infamous TI-99/4 home computer of the late 70s, with 32+6KByte ROM and 8KByte RAM. | ||
The firmware consists of mask ROMs, an FPLA, and patch EPROMs. These ROMs (particularly the early ones from Mostek) are a common point-of-failure. Several remedies exist, [[ | The firmware consists of mask ROMs, an FPLA, and patch EPROMs. These ROMs (particularly the early ones from Mostek) are a common point-of-failure. Several remedies exist, see the [[7854/Repairs|Repairs]] page. | ||
==Software== | ==Software== | ||