Re: PET Screen editor with phantom screen

I am not sure if it would work. First FFCF dispatches to the different devices 
as defined by a previous call to CKOUT at $FFC9.
It may depend on the editor ROM though.

The BASIC 1 (ok, deprecated, but I looked at it first accidently) does not have 
a redirection vector, see 
http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/pet/d/rom-1.html

In the BASIC4 editor, as given here 
http://www.zimmers.net/anonftp/pub/cbm/firmware/computers/pet/d/petdis
you can find that FFCF looks up the "default" or screen/keyboard input, to jump 
to $E116 in that case. Here there is a redirection vector on $00E9 that is 
used and that you can change.

In general, it is possible. I wrote a complete PET editor that completely 
replaced the screen handling with a serial (RS232) interface. So there are no 
special dependencies on screen editor variables outside the editor (I think).

André


On Sunday 18 May 2014 15:56:56 you wrote:
> Is it possible to fake out the screen editor on the PET, by manipulating
> the pointers on the zero page? The idea is to use CHRIN ($FFCF) to get a
> line of text from a part of PET memory that is somewhere else not in video
> memory ($8000-$83E7).  I think this is the setup, but there's a lot going
> on in the screen editor with quote mode etc...
> 
>     lda #3      ; Screen = device 3
>     sta $af     ; DFLTN Default Input Device = screen
>     lda #$0
>     sta $c4     ; PNT pointer - current scren line address
>     sta $c6     ; PNTR cursor column on current line
>     lda #$7c
>     sta $c5     ; PNT
>     lda #39
>     sta $d5     ; LNMX physical screen line length
> 
>     jsr CHRIN
> 
> The idea is to use CHRIN ($FFCF) to get a line of text from a part of PET
> memory that is somewhere else, and isn't in video memory ($8000-$83E7)
> 
> My early experiments indicate that it just might work.  Does anybody have
> knowledge or experience of this approach?


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