NXP Semiconductors Kinetis KE1xZ256, Reference Manual

Page: 632 / 1325

After all data values are written, the CRC result can be read from this data register. For a
16-bit CRC result, if transpose options 10 and 11 is used, the resulting value after
transposition resides in the CRC[HU:HL] fields.
This section shows two examples of using CRC module to implement typical CRC
algorithms, including both 32-bit and 16-bit algorithms.
30.4.1 32-bit POSIX CRC
CRC-32/POSIX: width=32 poly=0x04c11db7 init=0x00000000 refin=false refout=false
xorout=0xffffffff check=0x765e7680
uint32_t checksum32, dataSize;
uint8_t data[] = "123456789";
uint32_t *data32;
// Transport Bytes for data write, as the CRC_DATA requires MSB write first
// No transport for checksum read, enable complement read as xorout not zero
CRC_CTRL = CRC_CTRL_TOT(3) | CRC_CTRL_TOTR(0) | CRC_CTRL_FXOR(1) |
CRC_CTRL_TCRC(1) | CRC_CTRL_WAS(0);
// write polynomial register
CRC_GPOLY = 0x04c11bd7;
// write pre-computed control register value along with WAS to start checksum computation
CRC_CTRL |= CRC_CTRL_WAS(1);
// write seed (initial checksum)
CRC_DATA = 0;
// deassert WAS by writing pre-computed CRC control register value
CRC_CTRL &= ~CRC_CTRL_WAS(1);
// write data
dataSize = sizeof(data);
// 8-bit reads and writes till source address is aligned 4 bytes */
while ((data) && ((uint32_t)data & 3U))
{
CRC_DATA = *data;
data++;
dataSize--;
}
// use 32-bit reads and writes as long as possible
data32 = (uint32_t *)data;
while (dataSize >= sizeof(uint32_t))
{
CRC_DATA = *data32;
+;
dataSize -= sizeof(uint32_t);
}
data = (uint8_t *)data32;
// 8-bit reads and writes till end of data buffer
while (dataSize)
{
CRC_DATA = *data;
data++;
dataSize--;
}
// read 32bit checksum result
checksum32 = CRC_DATA;
Usage Guide
Kinetis KE1xZ256 Sub-Family Reference Manual, Rev. 3, 07/2018
632 NXP Semiconductors