Re: Interesting IEEE Code in VIC-1112

Jim,
Question: is the dead code due to bad branching etc?
(just a guess),  I assume this is ML.

Interesting Im adding this to my ML prg notes.

Im horrible at ML but this is good info Jim thanks.

Terry Raymond


On Friday, March 11, 2016, Jim Brain <brain@jbrain.com> wrote:

> IN this forum post:
>
>
> http://www.sleepingelephant.com/ipw-web/bulletin/bb/viewtopic.php?f=2&t=7855
>
> Simon Rowe has disssembled the code in the VIC-1112 adapter.  I think it
> is interesting how much dead code is in the listing:
>
> echkout    jsr fndflno        ; find file
>     beq lb0bf        ; branch if file found
>     jmp fe_ntopn        ; do file not open error and retirn
> lb0bf    jsr setflch        ; set file details from table,X
>     lda fa            ; get device number
>     bne lb0c9        ; branch if device is not keyboard
>     jmp fe_ntout        ; do not output file error and return
> lb0c9    cmp #$03        ; compare device number with screen
>     beq lb0d2        ; if screen save output device number and exit
>     bcs lb0d6        ; branch if > screen, IEEE bus device
>     jmp $f321        ; jump to KERNAL to handle RS-232 and tape
> lb0d2    sta dflto        ; save output device number
>     clc            ; flag ok
>     rts
> lb0d6    jmp lb0e8        ; skip dead code
>
>     nop            ; *** dead code ***
>     jmp $f332        ; *** dead code ***
>     cmp #$09        ; *** dead code ***
>     bne lb0e8        ; *** dead code ***
>     jsr lb59d        ; *** dead code ***
>     sta dflto        ; *** dead code ***
>     clc            ; *** dead code ***
>     rts            ; *** dead code ***
>
> lb0e8    jsr lb40c        ; command an IEEE device to LISTEN
>     sta dflto        ; save output device number
>     clc            ; flag ok
>     rts
>
> The author of the post conjectures that the code was lifted from somewhere
> else, like the PET.  Anyone recognize any of the dead code?
>
> Jim
>
>
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>


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