[Coco] replacing main rom

[jdaggett at gate.net]

Art

Currently I do not have a Coco 3 setup due to space limitations. Hopefully within the 
next two months that problem will be resolved somewhat. 

I can agree with the fact that the character blink timer is in the GIME chip. The 
Basic ROms code has no control over character blink. Furthermore you maybe right 
that the GIME chip does use the timer to control character blink attribute. Yet I have 
some reservations. What has my concern is that the timer is a 12 bit timer. That 
yields the max count of 4096. Setting the TINS bit sets the frequency in to the timer 
at high freqency. Clear teh bit and the timer input frequency is the slow frequency. 
There are two sources that specify two different frequencies for fast frequency, 279 
nS and 70nS. Irregardless this frequency input would yield a blink rate far to fast to 
be noticable. There has to be other hardware in the GIME chip to dived that input 
further down.  Even at slow frequency the timer counts down every 260.1 mS. 
Twice that is slightly longer than a  half second. 

Also it has been reported that writing $00 to $FF94 stops the timer? I fthat is so then 
the character blink would likely stop if the GIME does use the timer. Also it would 
seem odd to have a timer that can be  used by software that is also used for another 
hardware function. That produces a conflict of usage or at least a restricted usage of 
the timer. That is one cannot use the timer if in HR text mode and have any 
characters blinking. 


james


On 11 May 2005 at 22:27, Arthur Flexser wrote:

Date sent:      	Wed, 11 May 2005 22:27:37 -0400 (EDT)
From:           	Arthur Flexser <flexser at fiu.edu>
To:             	CoCoList for Color Computer Enthusiasts 
<coco at maltedmedia.com>
Subject:        	Re: [Coco] replacing main rom
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> My memory was not quite right on this;  it is the blink rate of
> characters on the 40/80 column screen that have the blink attribute
> selected, and not the cursor blink, that uses the GIME timer.  I
> believe this is effected in hardware rather than in the Basic ROMs. 
> You can demonstrate that the timer is used, though, by setting the
> timer input select bit (bit 5 of $FF91), which controls whether a
> "tick" of the timer is 63 microseconds or 279 nanoseconds, and looking
> at the effect on the blink rate of such characters.
> 
> Art
> 
> On Wed, 11 May 2005 jdaggett at gate.net wrote:
> 
> > Art
> > 
> > My search through the code has yielded no such usage of the timer by
> > the Super Extended Code at all. I also do not see where there is any
> > patch in the blink routines to allow for the GIME timer to control
> > the blink time. 
> > 
> > I maybe wrong and have not found any reference to the GIME timer
> > usage though.
> > 
> > This does seem to support the basic belief that the GIME timer was
> > for program development for games or other means.
> > 
> > james
> > 
> > 
> > 
> > On 11 May 2005 at 15:33, Arthur Flexser wrote:
> > 
> > Date sent:      	Wed, 11 May 2005 15:33:47 -0400 (EDT)
> > From:           	Arthur Flexser <flexser at fiu.edu>
> > To:             	CoCoList for Color Computer Enthusiasts 
> > <coco at maltedmedia.com>
> > Subject:        	Re: [Coco] replacing main rom
> > Send reply to:  	CoCoList for Color Computer Enthusiasts 
> > <coco at maltedmedia.com>
> > 	<mailto:coco-
> > request at maltedmedia.com?subject=unsubscribe>
> > 	<mailto:coco-
> > request at maltedmedia.com?subject=subscribe>
> > 
> > > On Tue, 10 May 2005 jdaggett at gate.net wrote:
> > > 
> > > > 
> > > > To my knowledge I am not sure that the Coco 3 rom uses the timer
> > > > for anything.
> > > 
> > > I seem to recall that the timer is used by Super Extended Basic
> > > for controlling the cursor blink rate on the 40/80 column screen.
> > > 
> > > Art
> > > 
> > > 
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> > 
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