Radio-86rk-monitor

Monitor for Radio-86RK (Retro Soviet hobbyist computer), Rewrited from Scratch, Well Described, Binary Identical to Original One.

I did the project because i would like to update hardware of "good-old" 8-bit PC, but it needs to update firmware. I did not found binary variants for my goals, i did not found sources for my modifications. Eventualy, i restored it from scratch by reverce enginering of the original binary file.

I described and commented it well enouth for future modifications and your education goals.

Tools for compile sources are

Tools for cross-compile sources are: https://github.com/vhelin/wla-dx

You may build it from sources for platforms:

Build Status - Linux
Build Status - macOS
Build Status - Windows x86
Build Status - Windows x64
Build Status - Windows MSVC

For Mac OS use: brew install wla-dx

Docs are here: https://wla-dx.readthedocs.io/en/latest/

The Monitor

The Monitor is a system programm with a command line interface, booted after System On or Reset. Monitor is placed in system's Read-Only Memory (ROM)

Monitor Commands

Memory Operations

    D<Start_Address>,<End_Address> - Display memory content in hexadecimal
    L<Start_Address>,<End_Address> - Display memory content in ASCII
    F<Start_Address>,<End_Address>,<Value> - Fill memory with the specified value
    M<Address> - Modify memory content
    T<Start_Address>,<End_Address>,<Destination_Start_Address> - Copy memory block to destination
    C<Start_Address>,<End_Address>,<Destination_Start_Address> - Compare memory block with destination
    S<Start_Address>,<End_Address>,<Value> - Search memory for a value
    R<ROM_Start_Address>,<ROM_End_Address>,<Destination_Start_Address> - Read from the ROM connected to the Parallel interface to memory

Run Control

    G<Start_Address>[,End_Address] - Run code, optionally stop at the specified address
    X - Display and modify registers
    U - Run Expanded ROM from 0F000h Address

Cassette Input/Output

    O<Start_Address>,<End_Address>[,Speed] - Write memory to cassette. Default speed is 1Dh / 1200 bps
    I[Offset][,Speed] - Read data from a tape to memory at the specified offset

The Monitor Tape Records

Monitor's format of a tape record:

0xE6 - Syncronization byte
XX XX - Start address of memory allocation, High byte First
XX XX - End address of memory allocation, High byte First
..... - Data of the file. Size of the file is END_ADDR - START_ADDR
00 00 - Junk bytes, may be absant
0xE6 - Syncronization byte
XX XX - Check summ, High byte First

The Monitor Memory Map

16K Version:
- 0000h - 3FFFh - SRAM
  - 3600h - 3FFFh - Display buffer and monitor variables
32K Version:
- 0000h - 7FFFh - SRAM
  - 7600h - 7FFFh - Display buffer and monitor variables
Both versions:
- 8000h - 8FFFh - 8255A PPI (Keyboard, Cassette recorder, Sound control)
  - 8000h - Channel A data
  - 8001h - Channel B data
  - 8002h - Channel C data
  - 8003h - Control word
- 0A000h - 0AFFFh - 8255A PPI (ROM Disk and Parallel Interface)
  - 0A000h - Channel A data
  - 0A001h - Channel B data
  - 0A002h - Channel C data
  - 0A003h - Control word
- 0C000h - 0CFFFh - 8275 CRT Controller
  - 0C000h - Data Register
  - 0C001h - Configuration / Status register
- 0E000h - 0EFFFh - 8257 DMA Controller (write only, because the computer architecture )
  - 0E000h - Channel 0 Address register
  - 0E000h - Channel 0 Lenght register
  - 0E000h - Channel 1 Address register
  - 0E000h - Channel 1 Lenght register
  - 0E000h - Channel 2 Address register
  - 0E000h - Channel 2 Lenght register
  - 0E000h - Channel 3 Address register
  - 0E000h - Channel 3 Lenght register
  - 0E000h - Configuration register
- 0F000h - 0F7FFh - Monitor Extention EPROM (read only)
- 0F800h - 0FFFFh - The Monitor EPROM (read only)

Monitor API

0F800h - Entry point after reset
0F803h - Keyboard input
- Input : None
- Output: A - character code read from keyboard
0F806h - Tape Read
- Input : A=0FFh - with sync; A=08h - no sync
- Output: A - data read from a tape
0F809h - Print character to screen
- Input : C - character to print
- Output: None
0F80Ch - Tape write
- Input : C - data to write
- Output: None
0F80Fh - Print character to screen (Duplicated entry)
- Input : C - character to print
- Output: None
0F812h - Query keyboard
- Input : None
- Output: A=00h - key not pressed; A=0FFh - key pressed
0F815h - Print to screen in hex
- Input: A - data to print
- Output: None
0F818h - Print string
- Input: HL - string address
- Output: None
0F81Bh - Get key
- Input : None
- Output: A=0FFh - key not pressed; A=0FEh - Rus/Lat; otherwise A - key code
0F81Eh - Get cursor position
- Input : None
- Output: H - row, L - column
0F821h - Read character from screen at current cursor position
- Input : None
- Output: A - char read from screen
0F824h - Read from a tape
- Input: HL - offset of memory buffer to store data to
- Output: HL - start; DE - end; BC - checksum
0F27h - Write block to a tape
- Input: HL - start, DE - end of memory block
- Output: BC - checksum
0F82Ah - Calculate Check Summ
- Input: HL - start; DE - end;
- Output: BC - checksum
0F82Dh - Init Display
- Input: None
- Output: None
0F830h - Get memory heap
- Input: None
- Output: HL - Address of highest address of memory, avalable for a user's programm
0F833h - Set memory heap
- Input: HL - Address of highest address of memory, avalable for a user's programm
- Output: None

Happy Hobying!

Valerii Grazhdankin

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