Re: emulation of a cbm8032 screen on a serial terminal (need some advices)

i have one of these http://www.brielcomputers.com/wordpress/?cat=11
and they use a avr8515 @ 16mhz  the 8080 runs about ~1.5mhz


----- Original Message ----- 
From: "Didier Derny" <didier@aida.org>
To: <cbm-hackers@musoftware.de>
Sent: Saturday, December 10, 2011 11:13 PM
Subject: emulation of a cbm8032 screen on a serial terminal (need some 
advices)


> Hi
>
> I'm thinking to the emulation of the cbm8032 screen on a pocketerm 
> modified
>
> I'thinking to modify the pocketerm as follow:
> - spi bus to communicate with the avr 128A1 xplained.
>  (apparently with the propeller it is possible to reach about 1 Mhz but 
> not
> beyond)
> - font modified in the propeller firmware to support commodore graphic
> characters.
> - font switching via a command send to the terminal.
> - keyboard code modified to create commodore codes
>  (not really worked on this par but I have a few idea coming from my old
> emulator)
>
> The fastest writing loop on the cbm screen is probably this sequence:
>
> Loop   sta $(xx),y    6  cycles
> iny            2  cycles
>       bne            3  cycles
>
> so a t 1 Mhz 83333 char /sec
> (1000000/12 * 10) = 833330 bits /sec   (8 bits + start + stop)
>
> if the addess change:  from the previous write
>  jocker + line + col
>
> but I guess that the writing in the screen is rarely random...
>
> while we are on the same line, we send the byte one after the others...
>   char + char + char
>
> but if the char is the same the char + a jocker + a rep count is sent.
>   char + escape code + rep count
>
> all write a not immediate but after a short time so there is a chance
> to create a string with a repeat count.
>
> My problem is the scroll, the scroll is really expensive, I'm thinking to
> Way to detect a scroll with a code not too expensive but without any
> Modification in commodore kernel.
>
> If I could find a way to detect it, I could send a scroll up/down command
> To the propeller
>
> Any idea for a scroll detection ?
>
> Thanks
>
> --
> Didier
>
>
>
>
>
>
>
>
>
>
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