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 the special 7B87 time base using real-time sampling. The project manager for the 7854 was Tom Rousseau. During early development, before it was given the name "7854", the product was referred to as the "Smart Scope", and the digital processing was called the "smarts".

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/Div
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 (P31) or 154-0893-09 (P11); 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
Options	Option 02: X-Y Phase Correction Option 03: EMC Modification Option 78: P11 Phosphor Option 2D: 4K Expanded memory storage for up to 40 waveforms and 2000 keystrokes

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, see the Repairs page.

Prices

Year	1981	1984	1990
Catalog price	$10,500	$14,230	$17,000
In 2021 Dollars	$34,300	$40,650	$38,600

Diagnostic Test Interfaces

• 067-0911-00 Diagnostic Test Interface
• 067-0912-00 Analog Test Card for 7854
• 067-0961-00 Diagnostic Memory Board

Extender Boards

• 067-0913-00 Extender Board 44-Pin (used with the A30-GPIB and A31-ROM Boards)
• 067-0914-00 Extender Board 80-Pin (used with the A27-MPU and A28-RAM Boards)
• 067-0915-00 Extender Board 124-Pin (used with the A26-Control Logic and A29-Display Boards)

Software

• Application Note 42W-5802, BASIC Software Programs for Communicating Between the 7854 and IBM PC, 1985 (OCR)
• 7854 software in BASIC
• FFT program

Links

• Talking to the 7854 Oscilloscope with TEK SPS BASIC in Handshake, Winter 1980/81
• Tek 7854 Design Team Note: The graduation cap on the Engineering Release cake (page 8) signifies that it is the "Smart Scope".
• Tek 7854 @ curiousmarc (with links to videos)
• Tek 7854 @ amplifier.cd
• 7854 ROMs, the whole story @ TekScopes groups.io
• Mostek ROM Repairs @ vintagetek.org
• overview of ROM repair options @ paulcarbone.com

Pictures

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  Tektronix 7854 with Waveform Calculator keyboard, 7A26, 7M13, 7D15, 7B87

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  7854 Front with 7A26,7B85,7B87

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  7854 Rear, older version

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  7854 Rear, older version, separate RAM and ROM boards, external battery backup, old-style, silent fan

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  7854 Rear, newer version, combined RAM and ROM boards, internal battery backup, new-style, less silent fan

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  7854 Top

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  7854 Left

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  7854 Right

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  Waveform Calculator Keyboard

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  Waveform Calculator Keyboard

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  inside the Waveform Calculator Keyboard

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  Digital section in the 7854

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  A2 Mode Switch

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  A2 Mode Switch

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  The A7 / Auxiliary regulator

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  A different revision of the A7 board

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  A11 Main Interface

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  A15 Signal Output

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  A15 Signal Output

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  A15 Signal Out Board

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  A17 Horizontal Amp Board

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  A18 Vertical Amp Board

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  A19 Vertical Channel Switch

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  A19 Vertical Channel Switch

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  A20 High Voltage

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  A21 Z-Axis

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  A25 Digitizer

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  A26 Control Logic Board

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  A26 Control Logic Board

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  A26 Control Logic Board

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  A27 MPU

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  A different revision of the A27 board

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  A28 RAM Board

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  A28 RAM Board with option 2D (RAM Expansion)

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  A29 Display Board

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  A30 / GPIB board

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  A30 GPIB, different revision

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  A31 ROM Board

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  A32 Rear Panel Connector

• 
• 
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  Picture of 7854 during development. Note the different measurement keyboard layout. Picture might date from late 1978

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  Picture of designing the 7854 waveform calculator keyboard. note the different Keyboard layout.

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  Alignment Pattern

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  Program for generating Alignment Pattern

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  Mainframe rise time measured with 067-0587-02

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  7854 diagnostics system with MicroLab I

Memory Maps

Devices with separated ROM and RAM boards (SN < B100000)

Address Range	Size	ICs	Purpose
0000...3FFE	8k	U100, U110	ROM
4000...7FFE	8k	U200, U210	ROM
8000...8FFE	2k	U300, U310	PATCH ROM “for future use”
9000...9FFE	2k	U400,U410	PATCH + ROM
			2k RAM	4k RAM	8k RAM
A000...A7FE	1k	U510,U520,U530,U540	x	x	x
A800...AFFE	1k	U610,U620,U630,U640		x	x
B000...B7FE	1k	U710,U720,U730,U740			x
B800...BFFE	1k	U810,U820,U830,U840			x
C000...C7FE	1k	U110,U120,U130,U140			x
C800...CFFE	1k	U210,U220,U230,U240			x
D000...D7FE	1k	U310,U320,U330,U340		x	x
D800...DFFE	1k	U410,U420,U430,U440	x	x	x
E000...E37E			GPIB, Keyboards, Digitizer,...
E380...FFFE			Reserved for Diagnostic Interface

Devices with combined RAM+ROM Board (SN >= B100000)

Address Range	Size	ICs	Purpose
0000...7FFE	16k	U220,U320	ROM
8000...9FFE	4k	U200,U300	ROM for future use
A000...DFFE	8k	U400,U410	RAM
E000...E37E	4k		GPIB, Keyboards, Digitizer,...
E380...FFFE			Reserved for Diagnostic Interface

Devices with installed Diagnostic Boards (all serial numbers)

Address Range	Size	ICs	Purpose
0000...0FFE	2k	U430,U330	ROM
1000...1FFE	2k	U410,U310	ROM
2000...2FFE	2k	U200,U100	ROM
3000...3FFE	2k	U220,U120	ROM
4000...4FFE	2k	U420,U320	ROM
5000...5FFE	2k	U400,U300	ROM
6000...6FFE	2K	U210,U110	ROM
7000...7FFE	2K		ROM for future use
8000...7FFE	4k		Not used
9800...9FFE			RAM in Microlab I, disabled when standard ROM is in 7854
A000...DFFE	2...8k		RAM – see tables above
E000...E37E			GPIB, Keyboards, Digitizer,...
E380...E39E			BKREGCS Breakpoint address register chip select
E3A0...E3BE			CTREGCS control register chip select
E3C0...E3DE			BKDATA breakpoint data latch
E3E0			F/P Display Data
E3E2			F/P Display Data
E3E4			F/P Keyboard Data
E3E6			F/P Keyboard flag reset
E3E8			Terminal I/O Control
E3EA			Terminal I/O Data
E3EC			Cassette I/O Control
E3EE			Cassette I/O Data
E3F0			Modem I/O Control
E3F2			Modem I/O Data
E3F4...E3FE			ONBDIO on board input/output to microlab I
E400...E7FE			RAM in Microlab I
E800...EFFE		U120,U225	ROM - bank switched by PROMBK
F000...FFFE		U220,U320	ROM - bank switched by PROMBK