Robotron PC 1715

A CP/M machine from East Germany, Robotron PC 1715 was used in many applications: As office computer, educational, programing, there were even versions with interface to program pacemakers. Some network interfaces also were built. Because it was made with elementary TTL logic it was quite reliable and replacement parts were easier to find. Unfortunately repairing was terrible, as there are dozens of these TTL circuits inside.
Robotron 1715 used only text mode. There were no graphic or sound capabilities, yet there were some prototypes of graphic mode expansion cards. Most CP/M software uses terminal configurations unusable with 1715. 1715 has 64K of memory, expandable to 256K with special expansion card. 256K units, PC 1715W (earlier schematics show name PC1715M, but there's some confusion with another model, this time with faster CPU clock), are rare and have additional floppy drive capabilities - you could boot only from first FDD, secondary had higher density and was able to read, write and format non-standard disks. They had also 4MHz clock.
Eariler PC1715 had 360K/400K disk drives. Next versions, where mostly 256K were manufactured, had one 800K drive (about 650K usable) and one 360K drive. Later produced 64K models had only higher density 800K (Quad Density) drives, these ones are the most popular units.

Here you can find a few photos from manufacturing plant!

Manufacturer VEB Robotron

Origin East Germany
Year of unit 1987
Year of introduction 1985
End of production 1989
Speed 2.25MHz
Colors: Monochrome
Sound: None
OS: SCP (CP/M clone)
SCP3 (CP/M 3 clone for 256K versions)
BROS - ??
JAMB - office management package in OS.

Display modes: Text: 64x16, 80x24
Graphic: none


Media: Embedded 2 5.25" FDDs.
External FDD.

Power supply:

Built-in switching power supply

I/O: Keyboard connector
Serial printer port (V.24 only output)
External disk drive port.
Possible upgrades: Cassette interface, not many more known.

Robotron 1715 units in Infosystem '88 show - source: IKS 1988. Because manufacturing of these computers in their early days was quite secret, it was once brought to computer show not as computer, but as printer driving machine. This minor change in papers satissfied bureaucratic requirements.

Software accessibility: Possible (CP/M),
Nearly impossible (dedicated)

I tracked my unit to Kovocas - now defunct (in fact in 2010) Czech factory making seltzer bottles. You can still see their web page in the Internet Archive. Software disk comes from JZD Agrotechnika Slusovice.

There are many models known, built to suit customers needs. Some contain modified character ROM to display cyrilic, German, Polish or semigraphic characters. It was impossible to just buy a Robotron privately, as it was very expensive, so purchasing a computer was only possible to authorities - and many of them had subsidized part of costs. On the other hand buying a computer (usually by national factory or cooperative) in times of applied socialism returned in first months, as optimized plans computed with database software gave bigger savings.
Earlier units had white case and have part of keys made of white plastic.

Ah, and the keyboard. There were 3 keyboard types:
 - Type 1 - with these plastic semi-transparend buttons on the right side of keyboard
 - Type 2 - with normal square buttons, but with round "heads" - something like in ZX Spectrum Plus.
 - Type 3 - with round-square buttons, every button had a small hollow to easier finger typing.
The keyboard is in fact a serial terminal transmitting device! It has its own micro-controlling circuitry, Z80B, EPROM etc.

If you have a K7637 (the one with lock plug on the right) keyboard, DON'T CONNECT IT TO 1715! You'll DESTROY all serial logic, rendering computer unusable!

One more curiosity: On the right you can see a postage stamp scan (from Wiki Commons) from 1987, issued in 30th anniversary of the "Messe der Meister von Morgen" - a young researchers competition and exhibition in German Democratic Republic.
The young student is using Robotron 1715 computer, where the computer in the backrgound is older Robotron A5120 (you can see it on another stamp), slower, with less memory, but compatible machine used widely to nearly everything requiring the computer - I saw one controlling a socks weaving machine manufactured in 1983. As I know today (2011) it still works well without any repairs.

Here's my attempt to describe mainboard.

Contents: Starting Recording media Serial boot Pinouts Links


It has VERY simplified ROM software. There's only one thing in there:
3. TRY SIO (undocumented!)
3. IF STILL NOT BOOTED (no disk, no SIO wakeup),  GO TO 1.

It means that when you turn it on, it should try to boot from floppy drive 1, then drive 2, and again drive 1, then drive 2... until you supply a system disk. Light should be lit on drive 1 then drive 2, then again drive 1 etc. The boot ROM won't display anything on screen. To briefly test CRT, try to turn it on with signal cable disconnected from computer. It should become green.

After floppy is placed in drive and drive is tried, Robotron should move drive's head back and forth. If the disk is good, it'll boot with one more head step. If it's totally different thing, it'll ignore the disk and go to another drive. If the disk is unreadable, it'll hang with black screen. If you are sure that disk is 100% OK, and Robotron only tries it and ignores it, it means that the problem is in drive or controller.

One more thing, which is quite important. If you disassemble your machine and see that there are 2 character EPROMs inserted in two sockets near display controller, not one EPROM and empty socket (and then display controller), it means that your Robotron has 2 character sets. It's quite frequent in non-German units. You can switch between these fonts using SI/SO key. After you press the key, LED will toggle. Pressing any other key will actually switch character sets.

Here are some ROMs to download:

Robotron 1715 system ROM (EPROM near CPU) - no. s502
Keyboard ROM (typical keyboard, no regionalized keys) - no. s600
Character ROM - primary, German, -  no. s619
Character ROM - secondary, Polish - no. s641
Character ROM - Russian Cyrilic - Probably primary and secondary. No idea which is which. - No.s605 and s643
Floppy controller ROMs - no. 068 and 069. These are installed as 1K ROMs, not EPROMs
Floppy controller ROMs ready to be burned in 2716 EPROMs for replacement.

If you don't want to fry EPROM with +12V and -5V, please, after programming, bend pins 19 and 21 upwards, then solder the wire to connect them to pin 24.

One more word of warning: There are 3 types of Floppy Controller Schreib-ROM or 069 FDC ROM (known as Write-ROM) on the Internet.
 - First has 1026 or 1027, but NOT 1024 bytes - it's bad, it was born as data transferring error on FTP site. Unfortunately it got to my site, now it's removed.
 - Second has 0x04 as first non-zero byte. I don't know, but my 2 ROMs don't have this and work. It is downloadable here, if you want to experiment with it.
 - ROMs in my website, they're confirmed they're OK (I had to replace Schreib-ROM with EPROM), but I don't know will they work with Your variant of Robotron. There were 2 variants of floppy controllers, I have one known as Var. 02.




Recording media, using CPA operating system.

Robotron 1715 uses a non-standard 720K 5.25" floppy discs called Quad Density. These disks spin at different speed and are magnetized weaker than High-density 1.2MB. Only 1.2MB High-density floppy drive can be used to write such disks in a PC.
It's easier to format a 360K disk to 800K than 1.2M to 800K. Why? Magnetization strength.
More, after you make a boot disk, you should know that Robotron is very picky about floppies used. Try with many, My unit booted from 6th or 7th floppy made with PC. Yes, 360K.

To make system floppy, use a PC with high-density (1.2MB) 5.25" floppy disk drive configured in BIOS as 1.2MB. DON'T USE 720K SETTING. Now you need pure DOS and 2 programs:
 - CopyQM
 - 22DSK and Robotron Disk Definitions
You should also grab:
 - A very limited boot disk image, contains some first-need programs in Russian.
 - Useful programs package. It's really minimal pack of useful programs, only few more than in a boot disk.
 - System Tools and Programming pack. They contain RAMTEST, BASIC, Fortran and few other utilities. Notice PMARC and PMEXT, it's an archiver. To extract PMA use PMEXT A:ARCHIVE.PMA A: (extracts to A:, you can use B:). CRUN is some kind of database. PCTEST is a Robotron testing tool.
 - A few other CP/M programs:
     - Spreadsheet
     - Text processor (already configured, try not to use TPINSTD, as it'll probably won't work)
     - Games package (One, name starting with N, I don't remember exactly, is not configured for Robotron and it won't work)
     - Database, version 1.0
     - Database, version 3.3
     - Database reporting tool ??

If you dare, here's a full dump of my boot (unfortunately it was unbootable) floppy from Czech Republic. I HAVE NO IDEA WHAT ALL THESE PROGRAMS ARE FOR!
There's a tool for reading DOS 360K disks on a Robotron, but I've never tried it!

Copy boot disk image to CopyQM directory. Now in pure DOS type:

copyqm b: /PLAYBACK=r1715.cqm

Now it should display a logo, ask for number of copies and write disk. Do not use CQMENU as it allows for non-direct controller access making the disk more unreliable.

This floppy should allow You to boot Robotron, format another floppies and make system floppies. This won't allow you to copy files, as it doesn't have a PIP utility, it should be copied to this disk (from my Useful Programs package) using PC and 22DSK utility.

To make another system floppy in Robotron booted from it (it's Russian written in Latin font):

A:init <----type init in prompt

Ukavi imq diskowoda: A    <----type drive to be formatted. You can use drive it was booted from, just swap floppies.

I don't remember next question (like vozmovnye formaty ... wyberi format), use 3 for the biggest floppy size.

Now it should ask something like "w n i m a n i e !  Wse fajly budut udaleny" (Warning! all files will be gone) - if you choosen boot drive, swap disks now and press Y.

vdi! idet formatizaciq! (01)    <--Wait, now formatting (track 01)

If you see:

o?bka!! ===> cboj dorovek!

it means track error. If it happens in the beginning, floppy may be unusable. Just remove it and reset computer, then insert bootdisk again. Most 1.2MB disks won't be formatted well in Robotron, giving this error in the beginning or in 30-55th track.

This shows end of formatting. Type any key to return to drive menu, Ctrl-C to exit:
konec formatizacii   (end of formatting)

Now let's install system: Type:


Then choose 2 (zagruzka aktiwnoj sistemy).

Now boot system is loaded to be transferred to floppy. Now choose 7 (zapisx SCP na disk - write SCP to disk) and choose newly formatted floppy drive, or swap it if using boot drive. Boot block is prepared. But system must be on a disk. Choose 5 (zapisx SCP w wide fajla - write SCP to file), type name of the command file ( or - if new disk is in B:), the disk should become fully bootable.

If you made error, and you must delete file, use ERA filename.ext command.
Display disk's contents using DIR.
TYPE filename.ext displays file contents.
Switch between floppies using A: or B: commands. Usually C: and D: are external 2 drives, if connected (but it can be changed with INSTSCP utility).

This OS is quite limited, as it doesn't have a PIP. PIP is the shell allowing file manipulations, for example copying:
Copies to In SC/P there are NO DIRECTORIES. You list the contents of current disk with DIR command. Change by A: or B: command.
Remember: PIP destination=source. NOT like in MS-DOS. It was made long time ago by programmers who were more familiar with such notation.

We must get PIP to the disk using our MS-DOS computer with 5.25" disk drive. Extract 22dsk, replace the definitions file with one suupplied in this page. Now you're ready to list, import and export files from Robotron disks. Just start CMENU in 22dsk directory, choose disk type, choose drive and you can go. Remember to type properly and, as you export from Robotron floppies, always export to existing directory. It won't create a new one but one big, unusable file.
Using 22DSK you can copy PIP and other programs/utilities available in the Internet (as CP/M software, not DSK disk image files) to Robotron floppies and back - read data from Robotron floppies to PC's hard disk. The only thing you should remember is that during importing files from Robotron disks 22DSK renames COM files to CPM. Just use "ren *.cpm *.com" in your disk dump's directory to get original names.
With 22DSK you can copy program packages from this site do disks, formatted in Robotron 1715. They should be made bootable by "zapisx SCP na disk" command, but they don't have to conatin SCP-DOS.COM file, as it's already in these packages.

During importing files from the Internet notice that:
 - Robotron has Z80 processor, not Intel 8086.
 - Robotron has non-standard display circuitry, so most western programs, even these with terminal configuration, won't work properly displaying garbage (or only cursor) on screen.
 - PMA files should be extracted in Robotron to a disk using PMEXT.





Serial port booting:

It is theoretically possible to override defective FDD controller and boot Robotron from serial port. The original page describing the process is gone, but some cites survived here, so here's a brief explaination in English:

1. Connect serial to PC. Parameters: 9600, 8-bit, 1 stop bit, Parity: Odd.
2. Turn it on or Reset. It'll query all drives and then serial port for booting signature.
3. Start sending "0x11 0x11" to serial port until you see "0x12 0x12" output. Then stop, as it's ready for taking program.
4. Send 0x0A 0x(start address low) 0x (start address high) of files. Probably also length of a file in the same format.
as I understand, there are two files you have to stuff in there: BIOS with CRT initialization and operating system.
After it there should be 0x0A, then start location in the discussed format.

As there's nothing to boot from, you should just check if it responds 0x12 0x12 to serial port (use only 3 wires connected nullmodem - GND (Robotron A1), Rx (Robotron B4) and Tx (Robotron A2)). If it responds and still doesn't boot, it means that FDC/memory (chips closest to keyboard connector are the lowest) is faulty or boot floppy is bad.
Exact pin configuration:

        Rx (to pin 3 of DB9)
|   *   *   *   *   *   *   * |
| *   *   *   *   *   *   *   |
  ^   ^
 GND  |
  |  Tx (to pin 2 of DB9)
 (to pin 5 of DB9)
(view from back of robotron)






Connector numbers - they are as in Service Manual. Terrible, but if you see it for long time, you'll get used to it.

What's going on with these "Pin x" numbers?
These pinouts are, or are designed to be, configurable by internal DIP switches. Not all pinouts go that way, some are just designed to it, but DIP switches have never been installed on mainboard and they're hardware-set default to some config. Many Robotron docs use "pin" notation instead of normal marking.

Keyboard connector:

1A - Clock
2B - +5V
3A - GND
4B - Data
5A - Shield


Printer connector:

1A - Pin 102 - Ground
2B - Pin 103 - TxD
3A - Pin 106 - CtS
4B - n.c
5A - Shield

IFSS connector, if expansion card installed:

1A - SD-
2B - SD+
3A - ED-
4B - ED+
5A - Shield


Serial V.24 connector has 13 pins, but naming goes the same way:

1A - Pin 102 - Ground
2B - Pin 101 - Protective ground
3A - Pin 103 - TxD
4B - Pin 104 - RxD
5A - Pin 105 - RtS
6B - Pin 106 - CtS
7A - Pin 107 - DSR
8B - Pin 108 - DTR
9A - Pin 109 - DCD
10B - Pin 111 - Signal rate selector
11A - Pin 113 - External transmit clock
12B - Pin 114 - ?Transmitted bit buffer?
13A - Pin 115 - Receiving clock 


Video output:

1A - Intensity
2B - GND
4B - Shield
5A - Video signal.


Monitor power supply:


1 - GND
2 - 12V DC
3 - Shield.

External floppy drive. I have no idea why numbering goes backwards, but I suggest you checking grounds with ohmmeter to be sure, because manuals of Eastern Block computers are full of mistakes:

No A B C





Links:  - Schematics, photos, scanned materials. - Technical resources. - Russian support page. Recently (2013) updated! Some stuff can be found mirrored in fileland. - German page about Robotron. - CP/M downloads - I recommend looking also at "Sonstige DDR Computer".