7854

The Tektronix 7854 Waveform Processing Oscilloscope, introduced in 1980, is a 400 MHz combined analog / digital mainframe in the 7000 series that takes two vertical and two horizontal 7000-series plug-ins. In addition to a conventional analog (real time) scope, it contains an equivalent-time sampling 10-bit digitizer and a programmable waveform processor with GPIB interface. Single-shot, pretrigger acquisition is possible with special 7B87 time base using real-time sampling. The project manager for the 7854 was Tom Rousseau.

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400 MHz waveform-processing scope

Produced from 1980 to 1990

Manuals

(All manuals in PDF format unless noted otherwise)

Manuals – Specifications – Links – Pictures

The waveform processor can be programmed using a detachable calculator-style keyboard, using postfix operators ("reverse Polish notation" like HP calculators) that operate on entire waveforms, not just individual numbers.

Key Specifications

Bandwidth	(analog) 400 MHz
Fastest cal. sweep	500 ps
Sample rate	500 kHz (stores repetitive waveforms up to 400 MHz)
Resolution	10 bit
Acquisition depth	128, 256, 512 or 1024 points
Memory capacity	2048 waveform points in up to 16 waveforms (optional expansion to 5120 points and 40 waveforms)
Single shot	events and pretrigger up to 50 µs/div ("2.5 µs/point") with the 7B87 Time Base
CRT	154-0644-05 (P-31) or 154-0893-09 (P-11); cathode −3 kV, anode +21 kV, distributed vertical deflection plates
Features	Signal Averaging Cursor measurements Waveform parameter measurements GPIB Interface (Standard) Waveform calculation operators - add, multiply, square root, log, abs Internal RPN programming language (Reverse Polish Notation) Keystroke Programming (Up to 2000 Keystrokes with Option 2D) programmable text display on screen

Internals

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. 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 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, outlined here.

Software

Prices

Year	1981	1990
Catalog price	$10,500	$17,000
2019 value	$29,360	$33,060

Links

Pictures

Tektronix 7854 with Waveform Calculator keyboard, 7A26, 7M13, 7D15, 7B87
7854 Front with 7A26,7B85,7B87
7854 Rear
Waveform Calculator Keyboard
Waveform Calculator Keyboard
Digital section in the 7854
A2 Mode Switch
A2 Mode Switch
A7 Aux Reg
A11 Main Interface
A15 Signal Output
A15 Signal Output
A15 Signal Out Board
A17 Horizontal Amp Board
A18 Vertical Amp Board
A19 Vertical Channel Switch
A19 Vertical Channel Switch
A20 High Voltage
A21 Z-Axis
A25 Digitizer
A26 Control Logic Board
A26 Control Logic Board
A27 MPU
A28 RAM Board
A28 RAM Board with option 2D (RAM Expansion)
A29 Display Board
A30 GPIB
A31 ROM Board
A32 Rear Panel Connector
7854 Top
7854 Left
7854 Right
7854 Rear
Picture of 7854 during development. Note the different measurement keyboard layout. Picture might date from late 1978
Picture of designing the 7854 waveform calculator keyboard. note the different Keyboard layout.