Writing a small test program - a bit off topic

Hi there!

I *hope* this mail isn't very off topic. In principle it probably is, but I don't know a mailing list which is about writing test programs to test processors in order to debug a hardware to get linux running. Plus, I suppose there are people out there who could help me. So I hope you won't stone me for this post.

Whatever:
I have to write some test program for a mpc875 processor. It should run in the processor cache as the memory of the hardware doesn't work for hardware-problem-reasons.

I set up the memory mapping of the IMMR of the processor with the debugger (BDM4GDB) so the IMMR is at 0xff000000.
Then I want to change the state of two leds. This can be done by writing some values into some memory-mapped MPC registers (PEDAT / PEDIR) which reside at IMMR + 0xac8 / 0xad8.

I wrote a C program to do that; As there is no OS I think I can just try to write to memory locations directly:

#define CONFIG_8xx

int main(void){
long* a;
long* b;
a = (long*)0xff000ac8;
*a = 0x00001800;
b = (long*)0xff000ad8;
*b = 0x00001800;
}

Actually, if I compile it (using Denx ELDK 3.1) with

ppc-linux-gcc -static led.c -o led

the resulting program is 477K big.
On the other hand, if I do

ppc-linux-as -mcom led.s
and
ppc-linux-as -mcom led.s -o led.bin

the resulting program is 439 byte big.

Now, my questions are: Will the 439 byte program faciliated this way do what I want? Did I make some fatal newbie mistakes? Does somebody know how to upload code to the mpc instruction cache and execute it?

Thanks for reading,

Peter Asemann

assuming 'foo.c' is your program, and you want to run it at origin 0.

Step 1) ppc8xx-linux-gcc -Dmain=_start -nostdlib foo.c -o foo

Step 2) ppc8xx-linux-objcopy foo -O binary foo.bin

Done!

Jason McMullan <[email protected]>
TimeSys Corporation