[Coco] replacing main rom

[Arthur Flexser]

Actually, at the fast timer rate, the blink rate does get so fast as to be
practically unnoticeable, as I recall;  the characters just take on a slight
flickering quality.  (The blink rate would be around 2 msec, which would indeed
be too fast to see, but the flicker may result from some sort of occasional
synchrony with the 60th of a second vertical refresh.)  You may well be right
that the 12-bit timer and the blink attribute timer merely overlap rather than
being entirely the same thing.

Art


On Thu, 12 May 2005 jdaggett at gate.net wrote:

> 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
> Send reply to:  	CoCoList for Color Computer Enthusiasts 
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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>
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> > > 
> > > > 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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