[Coco] Another speed question

[Becker, Gary]

Thanks everyone for the comments / suggestions. I am getting ready to do
a 6551 because I want a serial mouse. And those drivers are already
written.

The main reason for using the 6850 was that I already had it from
another project and know it worked. But if I replace the 6850 with a
6551, then I have to re-write my DECB routines as well as the NitrOS-9
drivers. But it would be more compatible and people with a real CoCo
could use the driver with their serial port.

There is no clear winner for me. But I can delay the decision until I
get the mouse working; then decide what to do.

On a side note; it is funny what drives people. I never intended on
implementing a mouse for NitrOS-9. The decision was made when I played
the Solitaire game under NitrOS-9. Even though I have much better games
on my workstation; the thought of playing this simple game is driving me
to create more hardware for my CoCo3FPGA. The game is useable with the
keyboard mouse, but a real mouse would make it much better.

Gary

-----Original Message-----
From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com]
On Behalf Of Kevin Diggs
Sent: Thursday, September 06, 2007 12:52 PM
To: CoCoList for Color Computer Enthusiasts
Subject: Re: [Coco] Another speed question

Hi,

	It has been a while since I made a stupid comment on this list
... so I 
guess it is about time?

	I assume this is for the FPGA thing. Is the 6850 compatible UART
an 
actual chip or is it code in the FPGA? (Since you mention "my 
implementation" I am guessing it is in the FPGA? ...) If it is just code

in the FPGA, how hard would it be to add a FIFO (asks the idiot who has 
never tried to play with FPGAs)?

					kevin

Becker, Gary wrote:
> I am using a UART compatible with the 6850, not the bit bang port. The
> 6850 has interrupt generation capabilities, but I have never tested my
> implementation. My driver does not enable the interrupt capability and
I
> intentionally disable CPU interrupts.
> 
> -----Original Message-----
> From: coco-bounces at maltedmedia.com
[mailto:coco-bounces at maltedmedia.com]
> On Behalf Of Gene Heskett
> Sent: Thursday, September 06, 2007 9:45 AM
> To: CoCoList for Color Computer Enthusiasts
> Subject: Re: [Coco] Another speed question
> 
> On Thursday 06 September 2007, Becker, Gary wrote:
> 
>>In a different thread, it was mentioned that the bit bang serial port
>>and the hires mouse adapter takes too much CPU time. I understand why.
>>Both devices use CPU timing loops and the interrupts have to be turned
>>off. This discussion caused me to think about the way that I am doing
>>the Serial Virtual Drive for the CoCo3FPGA under NitrOS-9. At the
>>present time, I turn off interrupts and poll the serial port until I
> 
> get
> 
>>the 256 byte sector. This takes approximately 25 mS. Since task
>>switching happens every 16+ mS, I am guaranteed to miss at lease one
>>interrupt. After the sector is received, I re-enable the interrupts. I
>>do this because I am afraid that I cannot service interrupts from the
>>serial port fast enough to keep up at 115200 bps. But I have never
>>tried.
>>
>>It would take a major rewrite of the driver to make it interrupt
> 
> driven.
> 
>>Is it worth the effort? Would it be better to lower the serial port /
>>drive speed to keep interrupts enabled?
>>
> 
> I don't believe this is possible due to where would one get the IRQ
> question?  
> If edge triggered, how many bit spaces have elapsed since the last
one?
> 
> One possibility that may or may not have been explored is that there
may
> be a 
> timer function in the gime, which could be programmed to fire an IRQ 
> everytime a bit time has elapsed, minus of course the exec time of the

> service routine itself.  Or on a repeat basis but how would one go
about
> 
> achieving the initial bit synch unless the start bit coming in was a
> separate 
> IRQ service routine to set that up, and then disable it till the stop
> bit 
> comes in.
> 
> I haven't looked at that recently, so I have NDI if its granularity
> could be 
> bent into a std rs232 timing stream.
> 
> 
>>Gary
>>


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