Chapter 7 ECC Generation Module (SRAM_ECCV3)MC9S12ZVMB Family Reference Manual Rev. 1.3NXP Semiconductors 2197.3.6 ECC AlgorithmThe table below shows the equation for each ECC bit based on the 16 bit data word.Table 7-11. ECC Calculation7.3.7 ECC Debug BehaviorFor debug purposes, it is possible to read and write the uncorrected use data and the raw ECC value directlyfrom the memory. For these debug accesses a register interface is available. The debug access is performedwith the lowest priority; other memory accesses must be done before the debug access starts. If a debugaccess is requested during an ongoing memory initialization process, then the debug access is performedif the memory initialization process is done.If the ECCDRR bit is set, then the automatic single bit ECC error repair function for all read accesses isdisabled. In this case a read access from a system memory location with single bit ECC error will producecorrect data and the single bit ECC error is flagged by the SBEEIF, but the data inside the system memoryare unchanged.By writing wrong ECC values into the system memory the debug access can be used to force single anddouble bit ECC errors to check the software error handling.It is not possible to set the ECCDW or ECCDR bit if the previous debug access is ongoing (ECCDW orECCDR bit active). This ensures that the ECCDD and ECCDE registers contains consistent data. Thesoftware should read out the status of the ECCDW and ECCDR register bit before a new debug access isrequested.7.3.7.1 ECC Debug Memory Write AccessWriting one to the ECCDW bit performs a debug write access to the memory address defined by registerDPTR. During this access, the raw data DDATA and the ECC value DECC are written directly into thesystem memory. If the debug write access is done, the ECCDW register bit is cleared. The debug writeaccess is always a 2 byte aligned memory access, so that no ECC check is performed and no single ordouble bit ECC error indication is activated.Table 7-10. SRAM_ECC Interrupt SourcesModule Interrupt Sources Local EnableSingle bit ECC error ECCIE[SBEEIE]ECC bit Use dataECC[0] ~ ( ^ ( data[15:0] & 0x443F ) )ECC[1] ~ ( ^ ( data[15:0] & 0x13C7 ) )ECC[2] ~ ( ^ ( data[15:0] & 0xE1D1 ) )ECC[3] ~ ( ^ ( data[15:0] & 0xEE60 ) )ECC[4] ~ ( ^ ( data[15:0] & 0x3E8A ) )ECC[5] ~ ( ^ ( data[15:0] & 0x993C ) )
