Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!uupsi!sunic!cs.umu.se!dvljrt
From: dvljrt@cs.umu.se (Joakim Rosqvist)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Copper & HiRes Interlace
Message-ID: <1991May25.165221.2209@cs.umu.se>
Date: 25 May 91 16:52:21 GMT
References: <4892@gumby.Altos.COM>
Sender: news@cs.umu.se (News Administrator)
Organization: Dep. of Info.Proc, Umea Univ., Sweden
Lines: 32

>When my software is in complete control of my Amiga 2000, I support my
>High Resolution Interlaced display by catching the Vertical blanking
>interrupt.  Essentially, my interrupt service routine looks like this:
>
>#define LOF 0x8000	/* Interlace Long Frame Bit */
>display_intr()
>{
>	if (custom.vposr & LOF)
>		custom.bplpt[0] = bitplane;
>	else
>		custom.bplpt[0] = bitplane + 80;
>	custom.intreq = INTF_VERB;	/* clear interrupt */
>}
>
>completely flip out every time I disabled interrupts.  The HRM states:
>
>  To get the Copper to execute the correct list, you set an interrupt to
>  the 68k just after the first line in the display.  When the interrupt
>  is executed, you change the contents of the COP1LC location register to
>  point to the second list.  Then, during the vertical blanking interval,
>  COP1LC will be automatically reset to point to the original list.
>

You will have use 2 copperlists, but you don't need any interrupt handling
to install it, the LongFrame bit can be written to as well.


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