NES（6502组装）精灵运动 [英] NES(6502 assembly) Sprites movement

问题描述

我目前正在开发NES（6502）组装游戏，但我不了解如何进行精灵移动。在这里，我认为它应该起作用：

I am currently working on a NES(6502) assembly game but I dont understand how to make a sprite move.Heres how I think its supposed to works:

(loop)
LDA $200 ;will load into the A register the content of address $200,wich contain the Y postion of my sprite
INA ;Increment the A register wich would increment the content of A wich is the Y position of my sprite..?

但是，您似乎无法递增A寄存器累加器，因为在尝试汇编时出现错误INA指令..所以我有点迷失了。我应该使用STA而不是LDA吗？但是我想使用地址$ 200的内容，而不要放置我选择的值。我不知道如何使我的精灵移动。

However it seems that you cannot increment the A register accumulator because I get an error when trying to assemble with the INA instruction..So Im a bit lost into that.Should I use STA instead of LDA? But I want to use the content of the address $200 and not place a value that I choose in it.I dont get how to make my sprite move.

谢谢！

推荐答案

实际上，对于在以下版本中使用的6502变体，没有 INA NES。您可以按照以下说明将 A 加1：

There's indeed no INA available on the variant of 6502 used in the NES. You can increment A by 1 using the following pair of instructions:

CLC     ; Clear carry
ADC #1  ; A = A + 1 + carry = A + 1

或者，如果其中一个索引寄存器为空您可以使用：

Or, if either of the index registers are free you can use:

LDX $200  ; or LDY
INX       ; or INY

但是请记住，其他算术运算，例如 ADC ， SBC ， LSR 等，无法在<$ c $上执行c> X 或 Y 。

Keep in mind, though, that the other arithmetic operations like ADC, SBC, LSR, etc, can't be performed on X or Y.

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