Avr ASM标签* 2 [英] Avr asm label*2

问题描述

我是avr asm编程的新手，在下面的示例中，我有几个问题:

Hi i am new in avr asm programming,in the example below, i have few questions:

1)它是标签:8位或16位长吗?

1) Is it label: 8 bit or 16bit long?

2)为什么需要乘以2的乘法标签?

2) Why multiplication label with 2 is needed?

3)指令LPM将其结果存储在寄存器R0中?如果是这样，那与Z有什么关系?

3) Instruction LPM is placing their result in register R0? If so, what does that have to do with Z?

4)您能否从提供的链接中解释引用的文本:

4) Can you explaine the quoted text from the provided link:

如果地址未乘以2并且标签位于字节地址0x60(字地址0x30)，则Z将指向存储在此处的代码.希望这可以解决寻址问题.其他版本是"

ldi ZL, low(2*label)
ldi ZH, high(2*label)

label:
.db "Hello world", 0
lpm

谢谢.

推荐答案

1. 标签是16位.
2. 因为汇编器正在使用字地址，但LPM需要字节地址.请注意，并不是所有的汇编程序都这样做，特别是avr-gcc使用的gas不会.那么您就不需要乘法了.
3. 是的，LPM的无操作数版本会自动加载到R0，并从Z获取地址.请参阅指令集参考.
4. 这还不是很清楚，但请参阅上面的#2.

1. Label is 16 bits.
2. Because the assembler is using word addresses, but LPM needs byte address. Note that not all assemblers do this, notably gas that's used by avr-gcc, doesn't. Then you don't need the multiplication.
3. Yes, the no-operands version of LPM automatically loads into R0, and it takes the address from Z. See the instruction set reference.
4. That wasn't too clear LOL, but see #2, above.

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