Getting started

Hi Luzie,

Thanks. These are useful links. I'd seen the first one before, but not the note about .128 mode being limited to use of NMI to load snapshots.

I can confirm that +3DOS commands (BASIC and m/code) do work from .128 mode, though any attempt to use the extended BASIC, or 'dot' commands in esxDOS, leads to a crash.

Currently, I'm just experimenting with DivMMC. I'd like to transfer some of my software onto SD card rather than diskette, to give my aging floppy drive a break. I've ported various tape-based games and programs to work from diskette. Sometimes it is just a case of updating the BASIC loader, though most games require a bit more work, and I end up writing a machine-code +3DOS loader.

Having got programs from tape to disk, I hope it is easier to get them onto DivMMC, though I need to work out what esxDOS calls are equivalent to +3DOS ones.

I realise I could just use TAP files or snapshots, though that seems less satisfactory and doesn't work so well for multi-loader games or programs.

It looks from other comments on the forum that there are a set of RST 08 hook codes for accessing esxDOS from m/code. Are they documented anywhere?

Thanks again,
Georgeo.

You should have a look here: http://board.esxdos.org/viewtopic.php?pid=1349#p1349
It´s for esxDOS 0.8.5, but you can see, what can be done with esxDOS via mcode.

It´s with all various disk-systems on the Spectrum (as they use there own syntax): You have to do convert every media-operation like load or save. I´ve seem approaches in MC for Betadisk/TR-DOS to place a BASIC-Line in TR-DOS-BASIC-Syntax in RAM and than call the BASIC ROM there to get it running.

From: https://cygnus.speccy.cz/popis_trdos-assembler.php

CHADD    equ    23645        ; Location of SOS variable CHADD
    ld    hl,(CHADD)    ; Start to save true CHADD
    ld    (TEMP),HL    ; Temporary store of true CHADD
    ld    HL,SAVE        ; Address of SAVE routine
    ld    (CHADD),HL    ; CHADD now points to our routine
    call    15619        ; ENTER TRDOS SAVE via chadd
    jp    BACK        ; Jump to program point from which the whole routine was called
    ld    HL,(CHADD)

    ld    (TEMP),HL    ; The routine for LOAD now repeats
    ld    HL,49500    ; the above with just the address
    ld    (CHADD),HL    ; changed.
    call    15619
BACK    ld    HL,(TEMP)    ; Start to restore CHADD
    ld    (CHADD),HL    ; Reload original CHADD
    ret            ; Return from where you came
TEMP    defs    2        ; Label allocating memory for temporary storage

SAVE    defb    234        ; code for REM
    defm    ":"
    defb    248        ; code for SAVE
    defb    34        ; code for "
    defm    "filename"
    defb    34        ; code for "
    defb    13

LOAD    defb    234        ; code for REM
    defm    ":"
    defb    239        ; code for SAVE
    defb    34        ; code for "
    defm    "filename"
    defb    34        ; code for "
    defb    13

If it "just games with multiloaders" you want to have on divMMC, I think you should have a look for .TRD-Diskimages with hacked games which support multiload. Those can e.g. be found on "Virtual TRDOS site" at: https://vtrd.in/games.php?t=a . They maybe run via TRDOS-Emulator of esxDOS.

Hi George,

yet I see there´s a problem with the code I post here:

It uses a CALL 15619 in the Betadisk/TR-DOS-ROM. This can´t be found in the Standard ZX ROM. And I don´t know, if/how esxDOS TRDOS-Emulator handles it...

I just have to try...

Hope to find some time today for this an will report back here.

Hi Luzie,

Sorry, I wasn't very clear. My plan is to try a simple load operation using the RST 0x08 hook codes which are listed in the Z88DK source code--e.g. call Open File, Read File, Close File, to see if the hook codes work. I can then try them from +3 BASIC mode, since I assume it is only the command parsing that doesn't work in +3 BASIC mode.

If it works, then I am in good shape for porting programs -- since it looks very similar to the way you access Microdrives, etc. from m/code.

I'm working on a real +3 for this, as I assume esxdos is not supported in many emulators, so I need to refresh my memory on how to use HiSoft Devpac first.

Thanks again,
George.

Hi AOwen,

Thanks. What triggers DIVMMC to activate? I know about NMI button and I assume RST 08 (like ZX Interface 1) but it sounds as if something else too? I was wondering how it intercepted BASIC load and save to tape operations.

Thanks again,
Georgeo.

Ah, okay. That is a much more extensive list of triggers than I expected, and explains why the device is so sensitive when running in +3 BASIC. I'll focus my machine code experiments on USR0 mode.

Thanks again,
Georgeo.