Hi,
I faced next issue that I've been studying for several hours and have
no idea why flash reads end up with incorrect value:
The function reading the data from flash is:
(gdb) list FlashReadByte
7 #include "uart.h"
8
9 uint16_t seg_cnt;
10
11 static inline uint8_t FlashReadByte(uint32_t address)
12 {
13 volatile uint8_t result;
14 volatile uint16_t sr, flash;
15
16 __asm__ __volatile__ ("mov r2,%0":"=r"(sr):);
// save SR before disabling IRQ
17 __dint();
18 __asm__ __volatile__ ("movx.a %1,%0":"=r"(flash):"m"(address));
19 __asm__ __volatile__ ("movx.b @%1, %0":"=r"(result):"r"(flash));
20 __asm__ __volatile__ ("mov %0,r2"::"r"(sr));
// restore previous SR and IRQ state
21 __eint();
22 return result;
// aligned address ->
low-byte contains result
23 }
Now, I am accessing flash at 0x14400 (82944d), this is the gdb session dump:
Breakpoint 24 at 0x45e0: file ../bootloader.c, line 22.
(gdb) monitor dis 0x14400 10
__ivtbl_64+0x4480:
14400: ff ff ff ff AND.B @R15+, 0xffff(R15)
14404: ff ff ff ff AND.B @R15+, 0xffff(R15)
14408: ff ff
(gdb) monitor dis 82944 10
__ivtbl_64+0x4480:
14400: ff ff ff ff AND.B @R15+, 0xffff(R15)
14404: ff ff ff ff AND.B @R15+, 0xffff(R15)
14408: ff ff
(gdb) continue
Continuing.
Breakpoint 24, FlashReadByte (address=82944) at ../bootloader.c:22
22 return result;
// aligned address ->
low-byte contains result
(gdb) print result
$62 = 85 'U'
As you can see the flash content at 0x14400 read by mspdebug is ff ff
..... while the 'result' variable says it's 85. Well, it's not :-)
Before, I was doing flash erases in the program, but suspected that
there might have been some flash access niuances, so now flash read is
the only operation that I do.
What am I missing here?
Best Regards,
Tomek
2014-05-05 9:34 GMT+02:00 Tomek Lorek <[email protected]>:
> 2014-05-04 22:14 GMT+02:00 Tomek Lorek <[email protected]>:
>> Just checked the flashdump diff right before and after executing the
>> program - "movx #0, @%0"::"r"(flash))" variant messed up the flash
>> bank A from where I was running the code and it erased 0xc400 instead
>> of 0x1c400.
>> Do you have any idea why?
>
> Ok, got it! I have misplaced the input and output operands:
> Correct: __asm__ __volatile__ ("movx.b #0, @%0":"=r"(flash):);
> Incorrect: __asm__ __volatile__ ("movx.b #0, @%0"::"=r"(flash));
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