topic Re: S32K312 CRC peripheral wrong result in S32K

S32K312 CRC peripheral wrong result

atranzillo93 — Mon, 25 Sep 2023 12:33:09 GMT

Hi, I'm trying to use CRC peripheral on S32K312 EVB. I need to calculate CRC of data in Program Flash and compare it with a precomputed checksum.

I'm using a tool to calculate CRC based on CRC-16-XMODE algorithm.

First of all I switch-on peripheral with this setting:

MC_ME_Type * const crcModeEntryInstance = IP_MC_ME;
crcModeEntryInstance->PRTN1_COFB3_CLKEN |= MC_ME_PRTN1_COFB3_CLKEN_REQ96_MASK;
crcModeEntryInstance->PRTN1_PUPD |= MC_ME_PRTN1_PUPD_PCUD_MASK;

crcModeEntryInstance->CTL_KEY = 0x5AF0U;
crcModeEntryInstance->CTL_KEY = 0xA50FU;
/* Poll partition update status */
while ((crcModeEntryInstance->PRTN1_PUPD & MC_ME_PRTN1_PUPD_PCUD_MASK) != 0u) {}

Then, I configure CRC peripheral as indicated on datasheet:

CRC_Type * const crcBaseAddr = IP_CRC;

crcBaseAddr->CTRL &= ~CRC_CTRL_TCRC(1UL);
crcBaseAddr->CTRL &= ~ CRC_CTRL_TOTR(1UL);
crcBaseAddr->CTRL &= ~CRC_CTRL_TOT(1UL);
crcBaseAddr->CTRL &= ~CRC_CTRL_FXOR(1UL);
crcBaseAddr->GPOLY = CRC_GPOLY_LOW(0x1021U);
crcBaseAddr->CTRL |= CRC_CTRL_WAS(1UL);
crcBaseAddr->DATA &= ~((uint32_t)CRC_DATA_LL_MASK);
crcBaseAddr->DATA &= ~((uint32_t)CRC_DATA_LU_MASK);
crcBaseAddr->CTRL &= ~(CRC_CTRL_WAS_MASK);

Since computation on flash doesn't work, I wrote a small piece of code to calculate checksum on 4 bytes and reduce entropy.

uint8_t vector[4u] = {0x03u, 0x04u,0x06u,0x09u};

static uint8_t data = 0xFFu;
static uint16_t crc = 0u;

for(uint8_t k=0u;k<4u;k++)
{
data = vector[k];
crcBaseAddr->DATA =CRC_DATA_LL(data);
NOP();
NOP();
}

crc = (uint16_t)(crcBaseAddr->DATA & CRC_DATA_LL_MASK);
crc = crc | (uint16_t)(crcBaseAddr->DATA & CRC_DATA_LU_MASK);

Result of CRC peripheral is E60F:

However, by using online calculator(as https://www.lddgo.net/en/encrypt/crc) I get 7C93.

I tried to change algorith and use other CRC settings but there is no way to get correct result.

Can you help to find the problem?

Do you know about any issue related to the use of CRC peripheral on S32K3xx uC?

Re: S32K312 CRC peripheral wrong result

VaneB — Tue, 26 Sep 2023 20:33:12 GMT

Hi @atranzillo93

I ask you to please test your code with just a value to verify the behavior.

I made a simple test using the Crc_Ip_Example_S32K312 and made the necessary changes to calculate CRC based on the CRC-16-XMODEM algorithm. The test result is a match between the code result and the CRC calculator you shared.

My recommendation is to take a look at this example, which you might find useful.

B.R.

VaneB

Re: S32K312 CRC peripheral wrong result

atranzillo93 — Wed, 27 Sep 2023 06:26:03 GMT

Hi, VaneB, by using just a value(the first one of the array, 0x03), the result is correct. But then it is wrong, maybe there is some errors in DATA register filling?

I try to look at RTD example even if it seems to compute CRC in a different way.

Thanks a lot.

Re: S32K312 CRC peripheral wrong result

atranzillo93 — Wed, 27 Sep 2023 12:36:33 GMT

Thanks for noticing me to look at RTD deeply. I found the problem: the filling of DATA register.

The right way is the following:

*(volatile uint8_t *)&crcBaseAddr->DATA = data;

In my code, instead I used this code:

crcBaseAddr->DATA = CRC_DATA_LL((uint8_t)data);

By replacing code, the CRC is as expected.