Re: Trying to understand the workings of a Memory Mapped I/O

Las wrote:
> Here is the sample area:
>
> #define P0 ((*(__R volatile unsigned char *)(unsigned char)0x0))
> #define P1 ((*(__R volatile unsigned char *)(unsigned char)0x1))
> #define P2 ((*(__R volatile unsigned char *)(unsigned char)0x2))
> #define P3 ((*(__R volatile unsigned char *)(unsigned char)0x3))
>
>
> How would you describe what this is or does? If someone could break it down
> so I could understand what is going on I would be in your debt.

Why would your teacher assign you something he had not discussed?

Anyway, when confused about declarations, read from R to L

// #define P0 ((*(__R volatile unsigned char *)(unsigned char)0x0))

// (unsigned char)0x0

You have a character constant of 0

// (__R volatile unsigned char *)

It is cast to a volatile pointer for some bad reason, and who knows what __R is,
because it is a user's macro.

// *(..)

Take the contents of the (nonsense) pointer.

// #define P0

Might as well compound the nonsense with bad practice by using a gratuitous macro.

Good luck on your homework.