Sample from a VBlank handler to transfer tiles using "popslide"

popslide.asm

    push de
    ld [wSP], sp
    ldh a, [hVRAMCopySrc]
    ld l, a
    ldh a, [hVRAMCopySrc+1]
    ld h, a
    ld sp, hl
    ldh a, [hVRAMCopyDest]
    ld l, a
    ldh a, [hVRAMCopyDest+1]
    ld h, a
    ld a, c
    cp 14
    jr c, .copyTile
    ld c, 14
.copyTile
    REPT 16 / 2 ; Copy 1 tile (16 bytes), 2 bytes per "block"
        pop de
        ld a, e
        ld [hli], a
        ld a, d
        ld [hli], a
    ENDR
    dec c
    jr nz, .copyTile
    ld sp, wSP
    pop hl
    ld sp, hl
    pop de
    jr c, .finishedVRAMTransfer
    ld hl, hVRAMCopyNbTiles
    ld a, [hl]
    sub 14
    ld [hli], a
    assert hVRAMCopyNbTiles + 1 == hVRAMCopyDest
    ld a, [hl]
    add a, 14 * 16
    ld [hli], a
    jr nc, .noCarry
    inc [hl]
.noCarry
    inc hl
    assert hVRAMCopyDest + 2 == hVRAMCopySrc
    ld a, [hl]
    add a, 14 * 16
    ld [hli], a
    jr nc, .doneVRAMTransfer
    inc [hl]
.doneVRAMTransfer