VELA - Expanding the VELA hardware

The VELA hardware was based around a Motorola 6802 processor (center) and had a basic support ROM (ISL1) built in as standard (bottom left) which carried the basic logging programs for the VELA machine as listed on the base of the VELA. You can click on the photo of the VELA circuit board to see a 6 mega pixel hi-res version.

The VELA circuit board showing the MC6802 and the EPROM ISL1

The VELA PLUS and RS Multi-Function Intelligent Data Logger shared the same PCB which you can see in the image below.

The VELA PLUS AND RS Multi-Function Intelligent Data Logger PCB

Early VELA PLUS devices were based on the VELA Mark II circuit board and added a noise reduction circuit on a daughter board into the path of the ZN449E A to D converter as can be seen in the photo below on the left of the photo.

VELA PLUS using a Mk II circuit board modified for reduced noise feeding the ADC chip

In addition to the ISL1 EPROM which carried the basic VELA system together with the initial programs 0 to 16, the VELA could be expanded with extra 2732 EPROMs which have a 4KB capacity to store programs for specialist applications. Some of the extra ROMs that were available were as follows:

  • ISL 2 - Utilities EPROM - Programs 17 to 39
  • ISL 3 - Graphics dump to printer EPROM - Programs 40 to 59 
  • ISL 4 - Physics EPROM - Programs 60 to 79
  • SAM4 - The supporting EPROM containing software to support the Sensor Adaptor Module
  • RS 1 - Equivalent to ISL1* for RS Components branded VELA - Programs 0 to 12
  • RS 2 - Extended Facilities ROM for RS Components branded VELA - Programs 20 to 28

The various EPROMs had several programs built in and their programming identification numbers and descriptions are as below.

ISL 1 - VELA System ROM - Programs 00 to 16

Program No. Program Description
00 Four channel voltmeter
01 Fast Analogue recorder (up to 3m20s)
02  Medium analogue recorder (up to 16m39s) 
03  Slow analogue recorder (up to 11d20h) 
04  Frequency Meter 
05  Event Timer 
06  Multi-chanel Timer 
07  Pulse counter (up to 41h37m) 
08  Statistics of inter pulse times 
09  Statistics of random events (up to 16m39s) 
10  Versatile waveform generator (uses the digital port) 
11  Control sequence generator (uses the digital port) 
12  Ramp generator 
13  Decimal to binary converter 
14  Dual beam oscilloscope
15  Data retrieve and transfer
16  User definable machine code program 

The base panel of the VELA with the ISL1 ROM program listing and hand written serial number

ISL 2 - Utilities EPROM - Programs 17 to 39

Only programs 20 to 27 were available. Selecting any other program number in this range simply called a RESET function to send a user back to the start point for programming the VELA.

Program No. Program Description
20 4 Channel Multimeter
21 Single Channel Fast Recorder
22 4 Channel Fast Recorder
23 4 Channel Slow Recorder
24 Re-entry to Display Routines
25 Single channel editor
26 Sensor initialisation
27 EPROM Identification Date

It seems that there are at least 2 different versions of ISL2 as the manual I have shows the following programs are available.

Program No. Program Description
17 Insert (into User defined program)
18 * Fast Data (Hex) Printer Dump (40 Col.)
19 * Print Data Table
20 * Disassembler
21 Display ADC Binary O/P codes
22 Variable Speed O/P to chart
23 Voltage to Frequency Converter
24 Music Box
25 100 µsec resolution timer
26 Memory Block Shifter
27 ** VELA Control by µComputer
28 4000 Byte (Secs) datalogger
29 Re-Entry routine
30 ** Download from µComputer
31 Save on Cassette recorder
32 Reload from Cassette recorder
33 * Fast Data Dump to 80/120 col. printers
34 * Print Data table 80/120 col. printers
35 * Disassembler for 80/120 col. printers
36 Hexadecimal User Creation
37 Binary to Denary Converter
38 Interactive Control Sequencer
39 *

Printer Primer 

Programs marked '*' require a centronics printer cable and suitable printer. Programs marked '**' require a suitable VELA to Micro cable.

ISL 3 - Graphics dump EPROM - Programs 40 to 59

ISL3 was scheduled for release in January 1985 was announced as containing Logic Tutor routines, Graphics Dump to printer and extra datalogging routines.

Program No. Program Description
40 4 channel logic analyser
41 ** Printout channel 1, fast transient recorder results
42 ** Printout 4 channel (msec) datalogger results
43 ** Printout 4 channel (secs) datalogger results
44 * Quad 2-input AND/NAND/OR/NOR simulation
45 * Dual 2-input AND, 2-input EOR, OR simulation
46 * Dual half adders, 2-input AND, OR simulation
47 * Quad Set-Reset Flip-Flops simulation


Triple JK Flip-Flops, Multi-input AND simulation
49 Ramp Generator and 4 channel sampler
50 *** Download Data/Program codes from Microcomputer
51 ** Printout a graph for fast transient datalogger
52 ** Printout a graph for 4 channel (msec) datalogger
53 ** Printout a graph for 4 channel (secs) datalogger
54 ** 4 channel (minutes) datalogger with printout
55 *** 4 channel datalogger controlled by Microcomputer
56 ** Printout data from Multi-channel timer (06)
57 ** Printout histogram for statistics (07)
58 ** Printout histogram for statistics (08)
59 ** Printout histogram for statistics (09)

Programs marked '*' require an Educational Electronics Logic board. Programs marked '**' require a centronics printer cable and suitable printer. Programs marked '***' require a suitable VELA to Micro cable.

I have no further information regarding this EPROM. If you have anymore information regarding this EPROM, please do get in touch.

ISL 4 - Physics EPROM - Programs 60 to 79

Program No. Program Description
60 Digital Volt Meter with movable decimal point
61 Digital Volt Meter (Decimal point and offset adjustable)
62 Digital Volt Meter (Offset adjustable and scaling)
63 Energy Meter
64 Power Meter
65 100uS resolution timer
66 Velocity Meter
67 Accelerometer via time measurements
68 Accelerometer via Dual velocities and time
69 Accelerometer - Direct readout
70 Digital Thermometer
71 Capacitance Meter
72 Phase Meter
73 Temperature Data logger
74 Rate Meter (0.1Hz resolution)
75 Two channel repetitive timer
76 Two channel velocity meter
77 Two channel timer and velocity meter
78 Variable LF Squarewave generator
79 Variable Sinewave oscillator (requires ISL3)

RS 1 - Standard EPROM - Programs 0 to 12

Program No. Program Description
0 Four channel digital voltmeter
1 Fast transient recorder
2 Analogue (transient) recorder
3 Analogue recorder, slow
4 Frequency meter
5 Event timer
6 Multichannel timer
7 Unassigned
8 Re-entry to output routines
9 Download from microcomputer
10 Waveform generator
11 Control sequence generator
12 User program creation

RS 2 - Extended Facilities EPROM - Programs 20 to 28

Program No. Program Description
20 4 channel sampling by microcomputer with real time data transfer
21 Data table to printer of data logging programs
22 Data table to printer of data logging programs
23 Data table to printer of data logging programs
24 Graphics output to printer of data logging programs
25 Graphics output to printer of data logging programs
26 Graphics output to printer of data logging programs
27 4 chanel real time logger to printer
28 Data table to printer of multi-channel timer

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If you've come across this page because you've found a dusty old VELA or any of the peripherals I've mentioned on the site in the store cupboard of the science department and you're wondering what you can do with it... You could always consider donating it to a good home such as mine where it would be reunited with a BBC Micro, archived for the future and used!

Although I now have many VELA related items, I am still missing many more bits and pieces so if you happen to have a VELA, any VELA software, manuals or related VELA handbooks, then I'd still be very interested in hearing from you so please do get in touch!

Of particular interest are any VELA SAM4 compatible modules and software for the RM380Z, Apple II and IBM-PC's of the day which currently are lost to the mists of time with the prospects of viable floppy discs containing the software being more remote as the years go by.

For a full list of VELA related items I'm looking for, please check out my VELA - WANTED, DEAD or ALIVE! page.

VELA Technical Downloads


The following ROM images are Mk I EPROMS and are incompatible with the ISL1* ROM from the VELA Mk II.  You can use the Mk I ROMs in a VELA Mk II or VELA PLUS but there are several differences in the data formats they produce when exporting from the VELA so when sending data to a microcomputer, it should be told it is connected to a Mk I VELA.

The following ROM images are for the VELA Mk II as indicated by a red *.

The following ROM images are for the VELA PLUS as indicated by a green *.

The following ROM image is for the SAM4 Sensor Adaptor Module

  • SAM* ROM

This final ROM is the RS Components ROM image that replaces ISL1* for their re-branded Multi-function Intelligent Data Logger.

IC Datasheets

The following datasheets cover all of the IC chips that are used in the VELA Mk. II data logger.


I'd like to thank Jon Neville-Green of The Discovery Academy School in Stoke-On-Trent who kindly arranged for me to obtain their VELA which had been gathering dust in exchange for a donation to the Science department at the Academy. Thank you very much.

I'd also like to thank Cathy Herriman of Sherborne School for providing me with a full surplus set of manuals and supporting books and documents for the VELA in exchange for a donation to the School funds. Thank you.

Finally, I'd like to thank Mr Robert Boyd of Glossop High School in Adelaide and Dr. Ashley Clarke (one of the original creators of VELA) who have both contributed information in various e-mails that has allowed me to build up and present a wider picture of the VELA data logger and what it could do.