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50hz.c
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1990-04-16
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3KB
Path: ux1.cso.uiuc.edu!brutus.cs.uiuc.edu!zaphod.mps.ohio-state.edu!wuarchive!mit-eddie!bloom-beacon!eru!luth!sunic!mcsun!hp4nl!phigate!philmds!ehviea!leo
From: leo@ehviea.ine.philips.nl (Leo de Wit)
Newsgroups: comp.sys.atari.st
Subject: Re: TECH: 50Hz and Boot Sector Booting
Message-ID: <527@ehviea.ine.philips.nl>
Date: 4 Apr 90 06:35:30 GMT
References: <16000032@ux1.cso.uiuc.edu>
Reply-To: leo@ehviea.UUCP (Leo de Wit)
Organization: Philips I&E Eindhoven
Lines: 83
In article <16000032@ux1.cso.uiuc.edu> cs325ec@ux1.cso.uiuc.edu writes:
|
|
| I was wondering if someone could answer two technical questions:
|
| 1.) 50Hz: Setting 0x448 to something other than zero does not
| put the ST in PAL mode, does it? I downloaded hertz.arc
| from terminator, but the hertz.tos is non executable,
| i.e. no 0x601a... I have seen both a boot sector program
| and a PD 50Hz program, but I can not find them now that
| I need to disassemble them.
You must flip some bit of the I/O registers to switch between 50 and 60
Hz (it is not used for the 70 Hz monochrome display).
When I bought my hard disk, I was told to get TOS in Rom, because
things wouldn't work OK (had a disk based TOS at that time). There
appeared to be something wrong with these Roms, at least for my (color)
display: flicker, a smaller (less higher) display and higher intensity.
Sometimes, especially after a (long) hard disk access, it would jump
into the correct mode (normal brightness, no flicker, normal display
height). After some time I found out the problem, i.e. the ST was
running in the wrong mode. I wrote a small program that flips between
50 and 60 Hz and can be put in the AUTO folder (it isn't even
resident). Here it is, with source code and uue-d program. Enjoy,
Leo.
-------------------------------------
******************************************************************************
* *
* swaphz.asm version 1.0 of 29 Oct 1988 (C) L.J.M. de Wit 1988 *
* *
* This software may be used and distributed freely if not used commercially *
* and the originator (me) is mentioned. *
* *
******************************************************************************
*
* NAME
* swaphz
*
* SYNTAX
* swaphz.prg
*
* DESCRIPTION
* Swaphz swaps - for low and med res - between 50 and 60 Hz.
*
module swaphz
section s.ccode
* system variables
syncmode equ $ff820a
* GEMDOS & (X)BIOS stuff
gemdos equ 1
super equ $20
swaphz
clr.l -(sp)
move.w #super,-(sp)
trap #gemdos
move.l d0,-(sp)
bchg.b #1,syncmode
move.w #super,-(sp)
trap #gemdos
lea.l 12(sp),sp
clr.w -(sp)
trap #gemdos
end
The program in uue form:
table
!"#$%&'()*+,-./0123456789:;<=>?
@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_
begin 644 swaphz.prg
M8!H @ $*G/SP ($Y!+P (>0 ! /^"z
7"C\\ "!.04_O Q"9TY! y
x
end