Control-A and other oddities

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Control-A and other oddities

Postby Kallikak » May Sun 07, 2006 1:18 am

Hi,

I noticed that typing control-A does a clear screen. Also, I noticed that:
Code: Select all
LDA #$01
JSR $FFEF
also clears the screen, while
Code: Select all
LDA #$02
JSR $FFEF

puts the cursor to the top left, but doesn't clear.

Is any of this consistent with a real Apple-1, or just an artifact of the Replica-1 video subsystem?

Ken
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Postby vbriel » May Sun 07, 2006 7:48 am

This is a replica 1 video subsystem. I needed a clear screen and home function on the replica 1 in software so I used null-characters that can't be typed. Only a few people (very few) have discovered this function 8)

Vince
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Postby foresmac » May Sun 07, 2006 8:32 am

Could that home function be used for ASCII animation? Since it doesn't clear the screen?

I guess along with that I wonder what the columns and lines of the video display are. I remember using a similar feature to program a sort of Galaga-esc game on my TI-81 in high school.

Mmmmmm...ASCII.
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Re: Control-A and other oddities

Postby daustin777 » Jan Sat 06, 2007 3:32 am

Kallikak wrote:
I noticed that typing control-A does a clear screen. Also, I noticed that:
Code: Select all
LDA #$01
JSR $FFEF
also clears the screen, while
Code: Select all
LDA #$02
JSR $FFEF

puts the cursor to the top left, but doesn't clear.


This isn't working for me on my replica se. Did something change?
-Dave
--David Austin-- replica 1 se, CFFA1, MicroKIM, [kits]
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Postby vbriel » Jan Sat 06, 2007 10:12 am

Yes, I put hidden control codes in the earlier versions of the video controller. It was a nice feature that I didn't think would act any different than the original apple 1. Well, the problem is that when you run the sample program in the apple 1 manual it tries to print every possible character and when it was hitting 0x01 which should have done nothing it would clear the screen. So I eliminated those characters and made sure that the replica 1 remains as close to the apple 1 as possible.

Vince
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