8.4.10 Error Correcting Code Testing (--ecc Options)

Error Correcting Codes (ECC) can be generated and placed in separate sections through the linker command file.

To enable ECC support, include --ecc=on as a linker option on the command line. By default ECC generation is off, even if the ECC directive and ECC specifiers are used in the linker command file. This allows you to fully configure ECC in the linker command file while still being able to quickly turn the code generation on and off via the command line. See Section 8.5.9 for details on linker command file syntax to configure ECC support.

ECC uses extra bits to allow errors to be detected and/or corrected by a device. The ECC support provided by the linker is compatible with the ECC support in TI Flash memory on various TI devices. TI Flash memory uses a modified Hamming(72,64) code, which uses 8 parity bits for every 64 bits. Check the documentation for your Flash memory to see if ECC is supported. (ECC for read-write memory is handled completely in hardware at run time.)

After enabling ECC with the --ecc=on option, you can use the following command-line options to test ECC by injecting bit errors into the linked executable. These options let you specify an address where an error should appear and a bitmask of bits in the code/data at that address to flip. You can specify the address of the error absolutely or as an offset from a symbol. When a data error is injected, the ECC parity bits for the data are calculated as if the error were not present. This simulates bit errors that might actually occur and tests ECC's ability to correct different levels of errors.

The --ecc:data_error option injects errors into the load image at the specified location. The syntax is:

The address is the location of the minimum addressable unit where the error is to be injected. A symbol+offset can be used to specify the location of the error to be injected with a signed offset from that symbol. The page number is needed to make the location non-ambiguous if the address occurs on multiple memory pages. The bitmask is a mask of the bits to flip; its width should be the width of an addressable unit.

For example, the following command line flips the least-significant bit in the byte at the address 0x100, making it inconsistent with the ECC parity bits for that byte:

The following command flips two bits in the third byte of the code for main():

The --ecc:ecc_error option injects errors into the ECC parity bits that correspond to the specified location. Note that the ecc_error option can therefore only specify locations inside ECC input ranges, whereas the data_error option can also specify errors in the ECC output memory ranges. The syntax is:

The parameters for this option are the same as for --ecc:data_error, except that the bitmask must be exactly 8 bits. Mirrored copies of the affected ECC byte will also contain the same injected error.

An error injected into an ECC byte with --ecc:ecc_error may cause errors to be detected at run time in any of the 8 data bytes covered by that ECC byte.

For example, the following command flips every bit in the ECC byte that contains the parity information for the byte at 0x200:

The linker disallows injecting errors into memory ranges that are neither an ECC range nor the input range for an ECC range. The compiler can only inject errors into initialized sections.