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FX-870P emulator

The program emulates the HD61700 microprocessor and uses the ROM dump from the original calculator, therefore it should function almost exactly like the real one.
It works on PC-compatible machines with Microsoft Windows operating system.

Files to download

Program version 12, updated 2023/12/15

fx870_es.zip - Delphi 5 sources

fx870_em.zip - compiled executable
Usage: extract the files into an empty directory, then run the program fx870.exe

fx870_fa.zip - alternative face image, contributed by Mahmoud Yassine
Usage: Replace the file face.bmp in the directory where the program was installed.

The screenshots

Usage hints

• Following files contain the memory images, and are loaded when the program is started:

    rom0.bin     - processor's internal 6kB ROM
    rom1.bin     - external 128kB ROM
    charset.bin  - LCD controller's internal character ROM of size 1.5kB
    ram0.bin     - 64kB RAM
    register.bin - processor's internal register file
  

• The updated files ram0.bin and register.bin are saved when the program is terminated. If they weren't found, they will be created. In such case the memory has to be initialised with the ALL RESET button.
• The emulator can be operated with the mouse or the keyboard. Special function keys:

    Cursor keys: corresponding arrow keys
    Page Up:     red S
    Page Down:   CAPS
    Esc:         BRK
    Insert:      INS
    Delete:      DEL
    Backspace:   BS
    Enter:       EXE
    F3:          suspends the code execution and opens the debugger window
    F4:          invokes the communication utility
    F9:          Reset

Integrated debugger

Disassembly box

• On entry, the starting address matches the Program Counter, but it can be modified by clicking on the address in the first line. New value must be confirmed with Enter.
• After clicking on a disassembled instruction, a new instruction can be typed. As with the starting address, pressing Enter accepts the changes. Only changes in the RAM area will be saved upon program termination, all ROM modifications will be lost. Characteristics:
  - labels and expressions aren't supported
  - accepted are hexadecimal (with the prefix &H) and decimal numbers
  - destination of relative jumps can be only specified as absolute address, not as displacement

Hex Editor box

• The HEX box allows viewing/changing the RAM contents only.
• It is possible to modify the starting address and the RAM contents by clicking on them. Enter accepts the changes.

Registers box

• The contents of the registers can be modified by clicking on them. Enter accepts the changes.
• The top line in the register box shows the state of the upper four bits of the Flag register. They can be modified as well.

Main register file box

• The contents of the registers can be modified by clicking on them. Enter accepts the changes.

Program execution control

• Closing the debugger windows resumes the program execution without tracing.
• Pressing the button [Run] in the Single step group box executes a single machine code instruction without servicing of the interrupts.
• To execute a specified number of machine code instructions type the required value to the field in the Number of steps group box, then press the associated [Run] button.
• The Breakpoint group box allows to specify condition that determine when the program execution should be interrupted. Currently it only compares the Breakpoint Address typed in the field with the Program Counter. When they match, the program execution is stopped and the debugger window reappears.

The fx870.ini file

Some parameters of the emulator can be customised by editing the fx870.ini file with any text editor.
Description of the contents of this file:

OscFreq = 921

This setting specifies the emulated CPU clock frequency in kHz.

Option2 = 0

This setting specifies the state of the port P4 (language version): 0 for the English FX-870P, 1 for the Japanese VX-4.

Uninstalling

To uninstall the emulator, simply delete the directory where it was installed. The program doesn't modify anything outside its installation directory.

Acknowledgments

• The program includes a freeware component ThreadedTimer developed by Carlos Barbosa.

Known limitations and issues of the current version

• The sound isn't supported.
• The scrolling function of the LCD controller command $8 isn't supported.
• Bugs may still lurk in the rom0.bin memory image.

Utilities

FMEM is a RAM image editing tool. It can display the usage status of ram0.bin and write/delete text files in the F0-F9 areas. It is also possible to load machine language files into FBF/VX-MENU with the attached Pbf2FM.b tool.