avr gcc内联asm变量输入操作数 [英] avr gcc inline asm variable input operand

问题描述

我希望能够在运行时确定内联asm函数的端口寄存器。

I want to be able to determine the port register for an inline asm function at runtime

asm(""::"I" (_SFR_IO_ADDR(PORTD)));

_SFR_IO_ADDR 只接受一个常量

我发现了这些选项，但似乎无法通过变量传递寄存器。

I have found these options but can't seem to pass register from variable.

asm(""::"m" (PORTD));
asm(""::"n" (&PORTD));

认为这是一个常见问题/要求，但似乎找不到任何答案

Thought this would be a common issue/request but can't seem to find any answers

推荐答案

AVR IN指令仅支持立即端口号。如果可用，您可能想尝试使用内存映射访问。 - 小丑

The AVR IN instruction only supports immediate port number. You might want to try memory mapped access instead, if available. – Jester

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