>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 01 September 2005 16:41
>To: Microcontroller discussion list - Public.
>Subject: Re: [PIC] Found difference between 16F628 and 16F628A
>
>
>On Sep 1, 2005, at 6:05 AM, Maarten Hofman wrote:
>
>> The EEPROM is used to house the user defined graphics. If a user
>> decides to
>> create their own graphic, they can send it to the system 
>using RS-232 
>> and it
>> is stored in EEPROM. However, while this is happening, the 
>system still
>> needs to update the TV screen (keeping synchronization is the most 
>> important
>> task of the system, everything else is secondary), and therefore 
>> access the
>> EEPROM if there are any user defined characters on screen.
>
>While I sympathize (somewhat, anyway) with highly tuned code 
>that has stopped working due to the differences between 628 
>and 628a, I gotta argue with your assumption there.  Surely 
>downloading user graphics happens seldom enough that you can 
>blank the screen while they are being saved to EEPROM?  I'm 
>reminded of the timex-sinclair zx80 that would blank the 
>screen a lot while running the basic interpreter.  It wasn't 
>great, but it was usable...

The ZX81 had a "fast" mode that blanked the screen and sped up basic execution by orders of magnitude.  The "slow" mode allowed display, but could only run the basic interpeter during horizontal retrace (IIRC).

Regards

Mike

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