Holy bitmask batman! A bug in Bensema's vcs.h!? It just goes to show you.
Never trust a constant that isn't all caps. ;-)
John
Eric Eid wrote:
> I had some difficulty adding uses for the difficulty switches to my Euchre
> game yesterday. I thought sure that I had the proper bit masks.
>
> I looked at the vcs.h I picked up at
http://www.io.com/~nickb/atari/doc/vcs.h
> and found this:
>
> ;
> ; Switch B equates
> ;
> SWCHB = $0282
> P0_Diff = $80
> P1_Diff = $40
> Con_Color = $08
> Con_Select = $02
> Con_Start = $01
>
> It's also the same in Glenn Saunders' proposed standards constants file,
> vcsc.h
(http://www.biglist.com/lists/stella/archives/200111/msg00427.html):
>
> ;DIFFICULTY SWITCHES
> P0_Diff = $80
> P1_Diff = $40
>
> In the ASCII version of the Stella Programmer's Guide
> (http://www.io.com/~nickb/atari/doc/stella.txt), the section on SWCHB
reads
> as follows:
>
> 4.1 Port B - Console Switches (read only)
> Port B is hardwired to be an input port only that is read
> by addressing SWCHB (HEX 282) to determine the status of
> all the console switches according to the following table:
>
> Data Bit Switch Bit Meaning
> D7 P1 difficulty 0 = amateur (B), 1 = pro (A)
> D6 P0 difficulty 0 = amateur (B), 1 = pro
> (A)
> D5/D4 (not used)
> D3 color - B/W 0 = B/W, 1 = color
> D2 (not used)
> D1 game select 0 = switch pressed
> D0 game reset 0 = switch pressed
>
> It looks to me like the values of P0_Diff and P1_Diff are switched around
in
> vcs.h.
>
> Am I reading this correctly or is there something I am missing?
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