At 19:53 25.02.99 -0500, you wrote:
>??? 1.? What does the line "org $F000" do?? It's one of the few lines
>that aren't commented.
It tells the assembler where to put the code. For example this is
nessessary to replace labels with the actual memory address.
If you have:
ORG $F000
ldx #$FF
LAB1: lda #$00
jmp LAB1
the assembler would know that LAB1 is at address $F002 and could replace
it in the JMP command.
>??? 2.? What's the difference between a "register" and an "address?"
A register usually is a memory address that interfaces with some other
hardware parts and makes them accessible for the programmer. For example
reading from memory address $F000 will give you whatever value is stored
there. Reading from memory address $0280, which is also the joystick port
register, will get you the current state of the joysticks.
Also the little memory inside the microprocessor, where the data gets
manipulated, is called registers.
>??? 3.? In Nick Bensema's "How to draw a playfield," under "Vertical
>Blank," it mentions machine cycles and includes the equation
>37*76=2888.? Now, my calculator says 2812 every time I punch it in.? Was
>this just a typo, or am I missing something?
I don't have the code here right now, but I guess that is just a little
typing error on Nick's calculator.
Ciao, Eckhard Stolberg
--
Archives (includes files) at http://www.biglist.com/lists/stella/archives/
Unsub & more at http://www.biglist.com/lists/stella/
