Robik: a ZX Spectrum Clone with a QWERTY Keyboard and RGB Output

ROBIK – A NEW INCARNATION OF THE ZX

The ZX Spectrum computer has not been manufactured for several years now, and, as a result, the number of its users is decreasing. This is a fact, and it will not be changed by the slightly better mechanical quality of Timexes and the Spectrum 128.

Unexpected help came to us from our “friends” across the eastern border. A copy of the ZX Spectrum called “Robik” was created in the city of Cherkasy. There would be nothing worth noting about this if not for the excellent quality of its keyboard—better than a PC’s.

The “Robik” keyboard is QWERTY type. It consists of 55 keys. It has dedicated Edit, 3 Shifts, a double Reset (for safety), Del, separate keys for the period and comma, as well as keys for selecting the Latin or Cyrillic alphabet. The methods for entering keywords and other characters are the same as on the ZX Spectrum.

The computer has a built-in Kempston interface, with dedicated keys for controlling it. This is very convenient for programs that are not games but use a joystick to move, for example, the cursor. However, there is one small problem: the computer has no high-frequency TV output or video output, only an RGB output.

It also has no edge connector, and all the I/O ports are DIN type, with 5 or 7 pins. And here comes a surprise. When you open the case, on the left side of the board you can see an unusual 64-pin male connector, to which all the signals are brought out.

       D6 * 1* +5V
       D4 * 2*
       D5 * 3*
      A11 * 4*
      A10 * 5*
      A12 * 6*
       D3 * 7*
       A9 * 8*
       A8 * 9*
       A7 * 0*
       A6 *11*
       A5 *12*
       D2 *13*
       A4 *14*
       A3 *15*
       A2 *16*
     RFSH *17* A1
       A0 *18*
       D0 *19* M1
    RESET *20*
      INT *21*
       D7 *22* NMI
    IORQE *23* WAIT
       WR *24*
     IORQ *25*
       RD *26*
       D1 *27*
   BUSACK *28* HALT
      A13 *29* BUSRQ
      A14 *30* ROMCS2
      A15 *31* ROMCS1
          *32* 0V

                 Connector view from
                 the outside

With a small modification, an edge connector can be attached, or, with a suitable card-edge plug, any peripheral can be installed.

The tape I/O is a 5-pin DIN connector. The socket, viewed from the outside, is numbered as follows:

              6 7
             1   2
              4 5
               3

The signal inputs and outputs are as follows:

  1-IN
  2-OUT
  3-GROUND

The RGB signal output is a DIN-5 connector, with the following pin assignments:

  1-R
  2-B
  3-G
  4-sync.
  5-sound

The DIN-7 monitor output allows you to connect an IBM-type monochrome monitor with a positive horizontal frequency of 18.432 KHz and a negative vertical frequency of 50 Hz, or an RGB color monitor. The pin assignments are as follows:

  1-R
  2-B
  3-G
  4-sync. ver.
  5-sync. hor.
  6-luminance
  7-video

The Kempston interface outputs use a DIN-7 connector:

  1-left
  2-down
  3-up
  4-fire
  5-right
  6-NC
  7-ground

The computer uses a Z-80 processor clocked at 3.5 MHz. Because it uses both the Cyrillic and Latin alphabets, when running programs that use interrupts, keyboard handling sometimes does not match the keys on the Spectrum. Apart from this inconvenience (about 5%), software compatibility is complete.

In conclusion, after making minor hardware adaptations, the computer is worth recommending, especially thanks to its excellent keyboard and almost 100% software compatibility.

Z.M.