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  • Re: "protecting" a section of color RAM

    From Sam Gillett@samgillett@msn.com to comp.sys.cbm on Tuesday, July 01, 2003 04:52:47
    From Newsgroup: comp.sys.cbm


    Roger Levy wrote ...

    the question is, what would be the easiest way to get the kernal ROM to >"stop" scrolling the colors upward at a certain line of the color RAM? the >c128 had a way to create a window, but i dont think c64 has that. this
    sucks. somebody?

    Sorry, I don't remember which issue it was in, but LoadStar published a
    Basic add-on that allowed using windows on the C64. Might not help you
    though as you are using Forth instead of Basic.

    Best regards,

    Sam Gillett aka Mars Probe @ Starship Intrepid 1-972-221-4088
    Last 8-bit BBS in the Dallas area. Commodore lives!





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  • From Roger Levy@trip_n_Save@hotmail.com to comp.sys.cbm on Tuesday, July 01, 2003 16:41:16
    From Newsgroup: comp.sys.cbm

    i was able get the job done with this code i wrote: (my thanks go to Paul
    for the helpful link)

    ; uses $10 and $11 of ZP
    lda #$00
    tay
    sta $10
    lda #$e0
    sta $11
    copy_kernal_ram_to_e000:
    lda ($10),y
    sta ($10),y
    clc
    lda $10
    adc #1
    sta $10
    lda $11
    adc #0
    sta $11
    bne copy_kernal_ram_to_e000

    ;switch rom out
    lda #$35
    sta $01

    ; set kernal to only scroll lines up to the following line#: reg_text_scroll_line=*+1 ;<----- i like to do this so the system is configurable from FORTH without using variables :)
    lda #20
    sta $e8f7

    ;of course, e000-ffff is now unusable. but if i ever discover more useful
    hacks for the ROM, now i know i can do it. :)


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