Elektronika BK-0011

2022-09-24

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Elektronika BK-0011 from 1989. This machine is successor of BK0010, same in english. Both use PDP clone-like CPU K1801WM1. The CPU is said to be fully compatible with PDP11 CPUs, but does not implement EIS instructions.

See articles in OldComputerMuseum,

PDP11 Instruction set

CPU runs at 4Mhz.
has 128KB RAM.
Monochrome/Color output via DIN connector.
Built-In speaker and (russian) keyboard.
Parallel and serial ports.
QBUS available at back side of case.
Slots for inserting additional option ROMs

Tape (cassette), Floppy and harddisk were somehow possible. Check this.

On arrival

The CPU KR1801WM1 (also KR1801VM1) (kyr.: KT1801BM1), date coded January 1990. Can address 64K Words, said to have 0.5 MIPS

KR1801WP1 (also KR1801VP1) (kyr.: КР1801ВП1), a gate array with 600 gates, close to the CPU

Another KR1801WP1 (kyr.: КР1801ВП1), close to keyboard connector

Used ROMs KR1801RE2: 4096x16 (64KBit)

After first cleaning

Main PCB

The keyboard element

Keyboard PCB with Speaker

Keys

ROMs

There are two locations for ROMs:

On main board
On ROM expansion PCB

ROM expansion PCB.

Next image shows ROM extension pcb. Two of the slots (the free ones) can be accessed by sliding the ROM cover at the case’s left side. Three other slots hold KR1801RE2 (kyr. KP1801PE2) ROM chips. In total, this PCB can hold 5 ROMs.

These three ROMs have id numbers 198,199 and 200. They are:

198 - Baseik BK-0011, 1st Chip
199 - Baseik BK-0011, 2nd Chip
200 - Baseik BK-0011, 3rd Chip

Baseik means BASIC.

ROMs on main board.

Two further ROMs are located on lower left corner of main board. These are also KR1801RE2 (kyr. KP1801PE2) ROM chips. The free socket above these two ROMs is the connector to the ROM expansion PCB.

These two ROMs have id numbers 201 and 202. They are:

201 - BC-0011 Monitor, 1st Chip
202 - BC-0011 Monitor, 2nd Chip

ROM content (to be researched)

The KR1801RE2 is a 64 KBit chip 4Kx16.

Information on content of many/all ROMs used for BK computers can be found here: https://github.com/nzeemin/bkbtl-doc/wiki/1801re2-ROMs-ru

From data sheet (I do not speak neither can read russian :-( )) I got some information on these chips. They need to be accessed in a special way.

To address 4Kx16 bit words, we need 12 bit wide addresses A0..A12.

The chips have no dedicated D0..D15 lines. The Address lines A0..A12 are also used for data, and so they are named AD01..AD12.

AD13..AD15 are used for some an id value (in range 0..7). The ROM only responses to requests if the id value at AD13..AD15 equals the value that was written during manufacturing. So BK-0011 can differentiate between 8 ROMs by this id.

To read, first the address must be written to the chip on AD01..AD12. Of course, the correct id need also be provided. This address is then latched by the chip. In a second step data can be read from AD0..AD15. The steps are controlled by /SYN and /RD lines, also by checking /AN output line.

If /RD=1 (write mode), the address is read into latch on falling edge of /SYN. While the ROM is reading in address and providing the data value, the ROM keeps /AN=1. When it finished the read step, it sets /AN=0. So /AN means data ready (AN stands for answer signal).

Then, by moving /RD=0 (read mode) and keeping /SYN low, we can read the data from D0,AD01..AD15.