[Coco] technical assembler question

[Mike Pepe]

Bob Devries wrote:
> Robert Gault said:
>> Probably depends on how often your code will do the BREAK test. You 
>> would not want several seconds to go by but the user is not likely to 
>> notice the difference of a poll every second vrs VSYNC intervals.
> 
> To do a break check on the VSYNC interrupt would mean I'd need to write 
> a bit of code to enable the VSYNC interrupt, and catch it, am I right?
> Then I would still need to do a check if in fact the break key had 
> activated my interrupt routine. My programme is I/O intensive (reading a 
> disk), but it seems slow to respond to the break key (at least in MESS).
> 

Disk I/O halts the cpu, and the internal loops must be run with 
interrupts disabled. So, yeah, your program will probably only be able 
to look for a break key between sector transfers anyway.

well, at least not without going to a lot of trouble



> -- 
> Regards, Bob Devries, Dalby, Queensland, Australia
> 
> Isaiah 50:4 The sovereign Lord has given me
> the capacity to be his spokesman,
> so that I know how to help the weary.
> 
> website: http://www.home.gil.com.au/~bdevasl
> my blog: http://bdevries.invigorated.org/
> 
> ----- Original Message ----- From: "Robert Gault" 
> <robert.gault at worldnet.att.net>
> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
> Sent: Thursday, May 17, 2007 11:37 AM
> Subject: Re: [Coco] technical assembler question
> 
> 
>> Bob Devries wrote:
>>> dear friends,
>>>
>>> I'm doing some writing in assembler for RSDOS (DECB). I don't do this 
>>> often, you understand, so I've got a question:
>>>
>>> When checking for a BREAK key, is it necessary yo do multiple reads 
>>> of the POLCAT routine to ensure the key is not missed? At the moment 
>>> i have this code:
>>>
>>> jsr [POLCAT]
>>> beq dskcont ;no key pressed, continue
>>> cmpa #BREAK ;that's #$03
>>> bne dskcont ;on BREAK, fall through to exit routine
>>>
>>> Should I loop through that a few times to be sure I don't miss it or 
>>> will that slow the programme down too much.
>>>
>>> What do the "experts" do in this case?
>>>
>>
>> Probably depends on how often your code will do the BREAK test. You 
>> would not want several seconds to go by but the user is not likely to 
>> notice the difference of a poll every second vrs VSYNC intervals.
>>
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