Banner Scroll with Screen Wrap

There are two easy ways to do what you want:
1) The easiest:
- Make sure your pattern is of length 32 bytes (which is the width of the screen in patterns)
- Have your pattern twice in your assembler file (so, 64 bytes, with the second 32 bytes being identical to the first 32)
- You then just copy 32 bytes to the screen, starting from the position 0, then in the next frame, from the position 1, in the next one from position 2, etc. once you reach copying 32 bytes starting from position 31, then you go back to position 0, and that's it.
2) Another method (a bit better), is to have the pattern only repeated once (so, only 32 bytes). But then you need to split your copy routine into two parts in order to simulate the "wrapping around" (which was simulated in the previous method by having the pattern repeated twice)

I hope that helps

Did you already try to program it in basic?

yes, but it helps you to prototype what you want. If it works (but slowly), you know the algorithms involved and what kind of VDP instructions you need.

Somehow I can not make the correlation between Z80 assembly language and basic.
BTW, I haven't a clue about any basic on the MSX.
I learned basic on the Apple 2 line of computers.
I have been learning Z80 assembly lately and this is just a stumbling block I asked for help with.

I don't have too many issues setting up and small time routines but for some reason just a scrolling banner with screen wrap has been complicated.

Ok, here's some example code on how to do it (just compile this to a ROM and run it). I assumed Screen 1, but the same should work in other tile-based video modes. I used the first simple method I mentioned above. I hope it helps

CHGMOD: equ #005f
LDIRVM: equ #005c
NAMTBL2: equ #1800   

    org #4000
    db "AB"     ; ROM signature
    dw Execute  ; start address
    db 0,0,0,0,0,0,0,0,0,0,0,0

Execute:
    ld a,1      ; Change screen mode
    call CHGMOD

loop:
    ld b,32
    ld hl,snake
loop_internal:
    halt
    push hl
    push bc
        ld de,NAMTBL2
        ld bc,32
        call LDIRVM
    pop bc
    pop hl
    inc hl
    djnz loop_internal
    jr loop


snake:
  db "------HEAD====BODY====TAIL------"
  db "------HEAD====BODY====TAIL------"