David Kelly wrote:
The cleanest way to pull this off would be to lay a structure on the
memory-mapped device and allocate it in a named section. See
http://gcc.gnu.org/onlinedocs/gcc-3.4.3/gcc/Variable-
Attributes.html#Variable-Attributes
Then in the linking stage define the location of the FPGA something like
this in Makefile:
LDFLAGS= -Wl,-Map,[EMAIL PROTECTED] \
-Wl,--section-start=.eeprom=0x00810001 \
-Wl,--section-start=.fpga1=0x6000 \
-Wl,--section-start=.hsa2d=0x7000 \
-Wl,--section-start=.sram=0x2000
Just use the __attribute__ to tag variables as section .sram and the
compiler will find places for them if you don't care about the order.
... Depending on your definition of "cleanest way". ;-)
If the FPGA will be updating these memory locations indpendent of the
code, then these will act a lot like processor registers. So, firstly,
you'll want to make sure that these memory locations are marked as
"volatile".
You can declare your variables similarly as registers are declared:
#include <stdint.h>
#define VARIABLE (*((volatile uint8_t *)0x1234))
...
VARIABLE = 0x01;
uint8_t foo = VARIABLE;
If you want to declare an array of uint8_t, then don't derefence the
pointer in the definition:
#include <stdint.h>
#define VARIABLE ((volatile uint8_t *)0x1234)
...
VARIABLE[1] = 0x01;
uint8_t foo = VARIABLE[1];
HTH
Eric
_______________________________________________
AVR-GCC-list mailing list
AVR-GCC-list@nongnu.org
http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
