topic about Jump from Flash to RAM code in Colilo. in ColdFire/68K Microcontrollers and Processors

about Jump from Flash to RAM code in Colilo.

Jiandong — Mon, 30 Oct 2006 16:08:04 GMT

HI Freescale,

the following code is in boot.S in Colilo. and I am confused with the Jump.

#ifdef CONFIG_COLILO_SOLO
move.l #0xFF800000, %a0 /* Colilo's in Boot flash */
#else
move.l #0xE0000000, %a0 /* Colilo's in Code flash */
#endif
move.l #0x1000000, %a1 /* RAM destination address */
move.l #0x7FFC, %d0 /* 32K long = 128 Kb */

loop_copy:
move.l %a0@+,%d1
move.l %d1,%a1@+
subq.l #1,%d0
bne.s loop_copy

move.l #real_start,%a0
jmp (%a0) /* Jump to colilo start address in RAM */ What this mean?? I think the #real_start is still in Flash. So didn't jump to the RAM.
#endif

/*
* Disable the cache. Don't want it on just yet.
*/
real_start:
jsr disableCache

jsr mcf548x_init
move.l #__SP_INIT, %SP

/*
* Most of the setup work is done in main().
*/
jsr start_main

Re: about Jump from Flash to RAM code in Colilo.

CompilerGuru — Fri, 03 Nov 2006 09:26:48 GMT

I dont know Colilo, but looking at the code it does make sence if
the labels are evaluated by the linker to RAM addresses.
Then the code before the JMP is assembled to a different address than it is executed from. The code starts out of flash, copies itself to RAM, and once this is done, it jumps there.
Can you decode/disassemble it and check to what #real_start actually evaluates, to a RAM or to a FLASH address?

Daniel

Re: about Jump from Flash to RAM code in Colilo.

Jiandong — Mon, 06 Nov 2006 10:04:23 GMT

After remap and code copying , the RAM remap to Flash address at 0x00000000, So #real_start is in Ram after.