NXP Semiconductors MPC5777M - Page 89

Testing All-X in RAM
Safety Manual for MPC5777M, Rev. 1.1
NXP Semiconductors 89
Figure 5 shows an alternative representation of the ECC encode process, written as a C language function.
Figure 5. C Language encodeECC function description
encodeEcc (addr, data_a2_is_zero, data_a2_is_one)
unsigned int addr; /* 32-bit byte address */
unsigned int data_a2_is_zero; /* 32-bit data lower, a[2]=0 */
unsigned int data_a2_is_one; /* 32-bit data upper, a[2]=1 */
{
unsigned int addr_ecc; /* 8 bits of ecc for address */
unsigned int ecc; /* 8 bits of ecc codeword */
/* the following equation calculates the 8-bit wide ecc codeword by examining
each addr or data bits and xor'ing the appropriate H-matrix value if the bit = 1 */
addr_ecc
= (((addr >> 31) & 1) ? 0x1f : 0x0) /* addr[31] */
^ (((addr >> 30) & 1) ? 0xf4 : 0x0) /* addr[30] */
^ (((addr >> 29) & 1) ? 0x3b : 0x0) /* addr[29] */
^ (((addr >> 28) & 1) ? 0xe3 : 0x0) /* addr[28] */
^ (((addr >> 27) & 1) ? 0x5d : 0x0) /* addr[27] */
^ (((addr >> 26) & 1) ? 0xda : 0x0) /* addr[26] */
^ (((addr >> 25) & 1) ? 0x6e : 0x0) /* addr[25] */
^ (((addr >> 24) & 1) ? 0xb5 : 0x0) /* addr[24] */
^ (((addr >> 23) & 1) ? 0x8f : 0x0) /* addr[23] */
^ (((addr >> 22) & 1) ? 0xd6 : 0x0) /* addr[22] */
^ (((addr >> 21) & 1) ? 0x79 : 0x0) /* addr[21] */
^ (((addr >> 20) & 1) ? 0xba : 0x0) /* addr[20] */
^ (((addr >> 19) & 1) ? 0x9b : 0x0) /* addr[19] */
^ (((addr >> 18) & 1) ? 0xe5 : 0x0) /* addr[18] */
^ (((addr >> 17) & 1) ? 0x57 : 0x0) /* addr[17] */
^ (((addr >> 16) & 1) ? 0xec : 0x0) /* addr[16] */
^ (((addr >> 15) & 1) ? 0xc7 : 0x0) /* addr[15] */
^ (((addr >> 14) & 1) ? 0xae : 0x0) /* addr[14] */
^ (((addr >> 13) & 1) ? 0x67 : 0x0) /* addr[13] */
^ (((addr >> 12) & 1) ? 0x9d : 0x0) /* addr[12] */
^ (((addr >> 11) & 1) ? 0x5b : 0x0) /* addr[11] */
^ (((addr >> 10) & 1) ? 0xe6 : 0x0) /* addr[10] */
^ (((addr >> 9) & 1) ? 0x3e : 0x0) /* addr[ 9] */
^ (((addr >> 8) & 1) ? 0xf1 : 0x0) /* addr[ 8] */
^ (((addr >> 7) & 1) ? 0xdc : 0x0) /* addr[ 7] */
^ (((addr >> 6) & 1) ? 0xe9 : 0x0) /* addr[ 6] */
^ (((addr >> 5) & 1) ? 0x3d : 0x0) /* addr[ 5] */
^ (((addr >> 4) & 1) ? 0xf2 : 0x0) /* addr[ 4] */
^ (((addr >> 3) & 1) ? 0x2f : 0x0); /* addr[ 3] */
ecc = (((data_a2_is_zero >> 31) & 1) ? 0xb0 : 0x0) /* data[63] */
^ (((data_a2_is_zero >> 30) & 1) ? 0x23 : 0x0) /* data[62] */
^ (((data_a2_is_zero >> 29) & 1) ? 0x70 : 0x0) /* data[61] */
NOTES:
1
Bit numbering is AHB convention, bit 0 is LSB. D[7:0] corresponds to byte at address 0. D[63:56] corresponds to
byte at address 7.