Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

IORD IOWR macros vs. memory access to peripherals

What is the point of the IORD and IOWR macros? I can access my custom Avalon peripherals using them, but it seems like I can't access them like the following: volatile alt_u32 *DEV_PTR = DEV_...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

You just mentioned the difference. The macros avoid the cache - volatile does not - it only hints to the compiler that the value is volatile and not to optimize reads or writes to the variable.

It works if you do this: 

volatile alt_u32 *DEV_PTR = alt_remap_uncached( DEV_0_BASE, sizeof( alt_u32 *) );
Bill A