Hi,
I'm trying to figure out how to properly erase (and then to write, but
this is the fist step to have anything working) flash region from high
memory (over 64kB), thus using 20-bit mode.
The erase procedure is quite straightforward:
--start--
unsigned long flash_addr = 0x1c400;
unsigned long flash;
unsigned int sr;
FCTL3 = FWKEY; // Clear Lock bit
while (FCTL3 & BUSY) ;
FCTL1 = FWKEY + MERAS; // Set MERAS bit
__asm__ __volatile__ ("mov r2,%0":"=r"(sr):); // save SR before disabling IRQ
__dint();
__asm__ __volatile__ ("movx.a %1,%0":"=r"(flash):"m"(flash_addr)); //
move 20 bit flash address from variable to a register
__asm__ __volatile__ ("clrx @%0"::"r"(flash)); // dummy write 0 (or
clrx) to the address contained in the register
__asm__ __volatile__ ("mov %0,r2"::"r"(sr)); // restore previous SR
and IRQ state
__eint();
while (FCTL3 & BUSY) ; // test busy
FCTL1 = FWKEY; // Clear MERAS bit
FCTL3 = FWKEY + LOCK; // Set LOCK bit
--stop--
This code does not work, I've been struggling with it for a couple of
hours and still miss what is wrong.
Disassembly looks like this:
--start--
unsigned long flash_addr = 0x1c400;
4458: b4 40 00 c4 mov #-15360,-10(r4) ;#0xc400, 0xfff6(r4)
445c: f6 ff
445e: 94 43 f8 ff mov #1, -8(r4) ;r3 As==01, 0xfff8(r4)
unsigned long flash;
unsigned int sr;
FCTL3 = FWKEY; // Clear Lock bit
4462: b2 40 00 a5 mov #-23296,&0x0144 ;#0xa500
4466: 44 01
while (FCTL3 & BUSY) ;
4468: 03 43 nop
446a: 1f 42 44 01 mov &0x0144,r15
446e: 1f f3 and #1, r15 ;r3 As==01
4470: 4f 4f mov.b r15, r15
4472: 4f 93 tst.b r15
4474: fa 23 jnz $-10 ;abs 0x446a
FCTL1 = FWKEY + MERAS; // Set MERAS bit
4476: b2 40 04 a5 mov #-23292,&0x0140 ;#0xa504
447a: 40 01
__asm__ __volatile__ ("mov r2,%0":"=r"(sr):); // save SR before disabling IRQ
447c: 0b 42 mov r2, r11
447e: 84 4b f0 ff mov r11, -16(r4) ;0xfff0(r4)
__dint();
4482: 32 c2 dint
4484: 03 43 nop
__asm__ __volatile__ ("movx.a %1,%0":"=r"(flash):"m"(flash_addr)); //
mov 20-bit flash address from variable to a reg
4486: 80 1f 5a 44 movx.a -10(r4),r10 ;0xffff6(r4)
448a: f6 ff
448c: 84 4a f2 ff mov r10, -14(r4) ;0xfff2(r4)
4490: 84 4b f4 ff mov r11, -12(r4) ;0xfff4(r4)
__asm__ __volatile__ ("clrx @%0"::"r"(flash)); // dummy write 0 (or
clrx) to the address contained in the reg
4494: 1e 44 f2 ff mov -14(r4),r14 ;0xfff2(r4)
4498: 1f 44 f4 ff mov -12(r4),r15 ;0xfff4(r4)
449c: 40 18 8e 43 clrx 0(r14) ;0x00000(r14)
--stop--
The address 0x1c400 is properly stored on the stack in -10(r4) (4458
and 445e). Then at 4486 it is mov'ed to r10, which is ok.
What happens in 448c and 4490? What is expected at -14(r4) and why is
the SR used in 4490 (mov'ed to r11 in 447c)? There is no C code
accompanying it.
I guess this is the problem as I can see in 448c and 4490 some strange
data to be written to the stack and when the clrx is called at 449c it
uses an indexed r14 with an offset of 0. I made a big mess :-)
Where is the issue in my code?
Using
__asm__ __volatile__ ("movx #0,&0x1c400");
works correctly, my goal was to make this address stored in a variable.
Thanks in advance for a hint!
Best Regards,
Tomek
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