I am just going to answer my own questions for future reference. I did some searching on the internet and came across this note on the the usenet comp.sys.powerpc.tech
http://newsgroups.derkeiler.com/Archive/Comp/comp.sys.powerpc.tech/2005-11/msg00015.html In summary, it performs a indirect jump to code via the CTR register. The following code snippet show how it is done. lis 9,0xFC00 /* Function is at 0xFC000000 */ mtctr 9 bctrl On Fri, Jul 18, 2008 at 4:29 PM, Tehn Yit Chin <[EMAIL PROTECTED]> wrote: > > Hi, > > This question is not directly related to linux, but a question on how to > execute code from. > > My test code is as follows.. > > void ram(unsigned int cat) __attribute__ ((section(".ram_code"))); > void ram1(void) __attribute__ ((section(".ram_code"))); > void flash(void) __attribute__ ((section(".text"))); > void flash1(unsigned int y) __attribute__ ((section(".text"))); > > void ram(unsigned int cat) > { > unsigned int abc; > > abc += 12; > abc += cat; > } > > void ram1(void) > { > ram(123); > } > > > void flash1(unsigned int y) > { > unsigned int x; > > x = x + y; > > } > > void flash(void) > { > unsigned int def; > > def += 12; > > asm (" bel ram1\n\t"); > } > > I have the section .ram_code mapped into the internal SRAM of the MPC55xx, > which starts at 0x40000000. Code in .text are mapped into MPC55xx's internal > FLASH, starting at 0x00000000. > > When I attempt to link the code together, I get the error > > U:\src\applications\comms/fatdog.c(35,1): relocation truncated to fit: > R_PPC_REL24 against symbol `ram1' defined in .ram_code section in > U:\src\applications\comms\fatdog.o > > I googled the error and I think it means that the ram1() is too far away and > the branch address has been truncated to fit into the binary. > > Other than assembler bel instruction, I have also tried bl, b and bea and all > of them gave the same link error. > > I was wondering if anyone can give some insight on how I can get the MPC55xx > to branch between FLASH and SRAM? > > Many thanks, > Tehn Yit Chin > _______________________________________________ Linuxppc-embedded mailing list Linuxppc-embedded@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-embedded
