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Recently I try to reverse piece of assembly code that written for C166/C167 Arch. But I have a problem with some places for convert to C code, such as:

loc_1892:
mov     r9, #4
add     r9, r0
mov     r12, #0FFFFh
mov     r4, r9
add     r4, #2
calls   0, sub_37C2
mov     r13, r4
mov     r14, r5
mov     r15, #6
calls   0, CRC_16_Calculate

and in sub_37C2 :

sub_37C2:
mov     r5, r4
shr     r5, #14
shl     r5, #1
mov     r5, [r5+0FE00h] ; ==> Or DPP0
bmov    r4.14, r5.0
bmov    r4.15, r5.1
shr     r5, #2
rets

also in CRC_16_Calculate:

loc_29A4:
mov     r4, r13
mov     r5, r14
add     r13, #1
addc    r14, #0
exts    r5, #1
movb    rl3, [r4]
movbz   r7, rl3

I guess in sub_37C2 code try to convert the near address to far. But I can't convert this to C code correctly. My CRC16 implementation shown below:

static uint16_t Crc16(uint8_t* cBuffer, uint16_t iBufLen, uint16_t wPreset)
{
    uint16_t temp;
    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;
}

As you see, I convert loc_29A4 to temp = *cBuffer++ where temp is uint16 but cBuffer is uint8_t

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  • What is your question?
    – Igor Skochinsky
    Commented Aug 26, 2020 at 17:34
  • Actually, I wanna to calculate the first address of an array that [r5+DPP0] pointing them.
    – Unicornux
    Commented Aug 28, 2020 at 11:12

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