Before that I asked about piece of code that used in this algorithm (here). Now I have a bit problem with the rest of algorithm.
So I have to describe this with detail. Sorry if i vast your time for read it.
I have shown an algorithm below. It seems is a CRC16 algorithm.
CRC_16_Calculate:
mov [-r0], r9
mov [-r0], r8
mov [-r0], r7
mov [-r0], r6
mov r9, r12
mov r8, r15
jmpr cc_UC, loc_29D6
; ---------------------------------------------------------------------------
loc_29A4:
mov r4, r13
mov r5, r14
add r13, #1
addc r14, #0
exts r5, #1
movb rl3, [r4]
movbz r7, rl3
movb rl6, #0
loc_29B4:
mov r4, r9
xor r4, r7
and r4, #1
jmpr cc_Z, loc_29C8
mov r4, r9
shr r4, #1
xor r4, #0A001h
mov r9, r4
jmpr cc_UC, loc_29CA
; ---------------------------------------------------------------------------
loc_29C8:
shr r9, #1
loc_29CA:
shr r7, #1
addb rl6, #1
cmpb rl6, #8
jmpr cc_C, loc_29B4
sub r8, #1
loc_29D6:
cmp r8, #0
jmpr cc_UGT, loc_29A4
mov r4, r9
mov r6, [r0+]
mov r7, [r0+]
mov r8, [r0+]
mov r9, [r0+]
rets
As you see in below I converted that to C++ code:
static uint16_t intCrc16(uint8_t* cBuffer)
{
uint16_t wPreset = 0xFFFF;
uint16_t iBufLen = 6;
uint16_t temp = 0;
while (iBufLen--)
{
temp = *cBuffer++;
for (uint8_t j = 0; j < 8; ++j)
{
if ((wPreset ^ temp) & 0x01) wPreset = (wPreset >> 1) ^ 0xA001;
else wPreset >>= 1;
temp >>= 1;
}
}
return wPreset;
}
It seems everything is good but the problem appear right here. The main loop of this function run for 6 times(iBufLen) but
the input argument(cBuffer) length is always 4 Bytes. To prove this point we check where this algorithm invoked. Look at below:
mov r13, r4
mov r14, r5
mov r15, #6
calls 0, CRC_16_Calculate
As you see, r13 and r14 are input argument as cBuffer and r15 equivalent to iBufLen.
So, what's my mistake?
By the way, r4 and r5 are the returned value of function that I pointed (here).
