7854

From TekWiki
Jump to navigation Jump to search
Manuals – Specifications – Links – Pictures

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.

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.

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

Diagnostic Test Interfaces

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)

Links

Pictures

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 Diagnostio 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