Re: Detect a C128 from C64 mode

On 2013-05-22, at 19:32, Greg King wrote:

> From: <silverdr; on Monday, May 20, 2013; at 4:50 PM -0400
>> 
>> ; Checks for the output of the additional C128 VIC register
>> ; at $d030. In a 64, it reads $ff. In a C128 in 64 mode,
>> ; it outputs other values, as it has the two bits controling
>> ; "test" and "clock speed" modes.
>> ;
>> ; INPUTS: none
>> ; RETURNS: C128 flag in .A
>> ; REGISTERS AFFECTED: .A
>> 
>> _c128_check:
>> lda $d030
>> cmp #$ff
>> beq c64
>> bne done_c128
>> c128:
>> lda #$ff
>> sta $d030
>> done_c128:
>> lda #$01
>> rts
>> 
>> c64:
>> lda #$fc
>> sta $d030
>> eor $d030
>> beq c128
>> done_c64:
>> lda #$00
>> rts
>> 
>> Any ideas to shorten it, keeping the same functionality?
> 
> You want it; you got it!
> 
> _c64_check:
>   asl $d030
>   ror $d030
>   lda #0
>   rol a
>   rts

Wow!! Now - that's a show-off (in the most positive meaning of the word).. max respect, Greg!

It reverses the meaning of the flag but.. no, I am all fine with this!
-- 
SD!
       Message was sent through the cbm-hackers mailing list