Path: chuka.playstation.co.uk!news
From: "Alex Herbert" <aherbert@ndirect.co.uk>
Newsgroups: scee.yaroze.programming.2d_graphics
Subject: Re: pmode in GsIMAGE
Date: Wed, 10 Mar 1999 21:34:57 -0000
Organization: PlayStation Net Yaroze (SCEE)
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Message-ID: <7c6ovr$cij10@chuka.playstation.co.uk>
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Rad wrote in message <7br8vg$l2g2@chuka.playstation.co.uk>...
>Actually that's a good question - why are the cases 0x08 and 0x09?
>I figured it had something to do with pmode being a signed short and the
>playstation's byte ordering being different.
>
>The only explanation I could come up with is that:
>hex        bin     dec
>0x08 = 1000 = 0
>0x09 = 1001 = 1
>and that the playstation interprets the most significant bit as a positive
>number.
>
>Anyone care to explain/correct?
>
>Thanks,
>Rad.
>rad@cyberdude.com
>http://www.netyaroze-europe.com/~radpsx
>


Hmm, that doesn't sound right to me.  That's not how the sign bit works.
Negative numbers have the sign bit set.

hex      bin      dec
0x0 = 0000 = 0
0x0 = 0001 = 1
0x8 = 1000 = -8
0x9 = 1001 = -7

This assumes that this is 4-bit signed, which is a bit odd in itself - the
sign is bit 7 of a byte (char), and bit 15 of a short.

Anyhow, this toubled me when I first started with the Yaroze.  I thought
that bit 3 indicated a mixed mode TIM, but I've just looked at the File
Formats PDF and that says that it's bit 4.  So, I don't know the answer.  My
solution was:

tim.pmode &= 0x0007;

just after the call to GsGetTimInfo().  This just masks off all the unwanted
bits.




Herbs