ZHCSEV8D March 2016 – January 2018 ADS131A02 , ADS131A04
PRODUCTION DATA.
Hamming code is an optional data integrity feature used to correct for single-bit errors and detect multiple-bit errors in each device word. Enable hamming code with M2 pin settings (see Table 10 for details). Tie the M2 pin to IOVDD through a < 1-kΩ resistor to enable hamming code, or tie the M2 pin to GND through a < 1-kΩ resistor to disable hamming code.
Hamming code is only supported in 24-bit and 32-bit device word sizes. The ADS131A0x outputs 24 bits of conversion data and an 8-bit hamming code per channel when operating in 32-bit word size. The ADS131A0x outputs 16 bits of conversion data and an 8-bit hamming code per channel when operating in 24-bit word size. Table 10 lists the configuration options of the M1 and M2 hardware pins and the associated device word size. The status and command words are always 16 bits in length, reserving the eight least significant bits for hamming code.
M2 STATE | M1 STATE | DEVICE WORD SIZE | CONVERSION DATA | HAMMING DATA |
---|---|---|---|---|
IOVDD | IOVDD | 32 bits | 24 bits | On: 8 bits |
GND | 24 bits | 16 bits | On: 8 bits | |
Float | Not available | Not available | Not available | |
GND | IOVDD | 32 bits | 24 bit + 8 zeroes | Off |
GND | 24 bits | 24 bit | Off | |
Float | 16 bits | 16 bit | Off | |
Float | N/A | Not available | Not available | Not available |
When enabled, the hamming code byte is an additional 8-bits appended to the end of each device word on both the input and output, as shown in Figure 58. This additional eight bits are a combination of five hamming code (Hamming) bits, two checksum (ChS) bits, and one zero bit, as shown in Figure 59.
CRC can be used with the hamming code error correction enabled. When the hamming code error correction is enabled with CRC, the 8-bit hamming data per device word is not protected by the CRC and is ignored in the calculation. For example, if the 32-bit word size is used with hamming code enabled, the CRC check only uses the most significant 24 bits of each device word and ignores the last eight bits used for the hamming code. The CRC considers each device word as being 24 bits.
Table 11 shows the hamming bit coverage for 24-bit data. The encoded data bit 00 corresponds to the LSB of the data and bit 23 is the MSB of the data. The hamming code bits are interleaved within the data bits. H0 is the least significant bit of the hamming code and H4 is the most significant bit.
HAMMING OR DATA | D | D | D | D | D | D | D | D | D | D | D | D | D | H | D | D | D | D | D | D | D | H | D | D | D | H | D | H | H | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Encoded data bits | 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 04 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 03 | 20 | 21 | 22 | 02 | 23 | 01 | 00 | |
Parity bit coverage | H0 | x | x | x | x | x | x | x | x | x | x | x | x | x | x | x | ||||||||||||||
H1 | x | x | x | x | x | x | x | x | x | x | x | x | x | x | ||||||||||||||||
H2 | x | x | x | x | x | x | x | x | x | x | x | x | x | x | ||||||||||||||||
H3 | x | x | x | x | x | x | x | x | x | x | x | x | x | x | ||||||||||||||||
H4 | x | x | x | x | x | x | x | x | x | x | x | x | x | x |