ADXL180
Rev. 0 | Page 25 of 56
TRANSMISSION ERROR DETECTION OPTIONS
There are two error checking methods available: a 3-bit CRC
and a 1-bit parity check. These are determined by the user-
selected Bit ERC.
Table 20. Error Check (ERC) Bit Options
ERC Definition
0
A 3-bit CRC is included in the message. CRC is calculated
using the polynomial x
3
+ x
1
+ x
0
. (Default.)
1
One parity bit is included in the message. CRC is not used.
It is a bit that is set such that even parity is achieved in
the transmitted message.
CRC Encoding
The ADXL180 can be programmed to utilize a 3-bit CRC. The
polynomial used for the encoding is x
3
+ x
1
+ x
0
. The CRC
calculation is performed from MSB to LSB on the entire data
frame. The CRC state registers are initialized to zero. Therefore,
when checking the result of the transmission, the final CRC
check state should be zero. The three CRC bits are always the
three least significant bits in the transmission.
Parity Encoding
The ADXL180 can be programmed so that the LSB of each data
transmission contains a 1-bit parity check bit. The 1-bit parity
check is even parity. The parity algorithm sets the parity bit to
be either a one or a zero; thus, the resulting number of ones
transmitted in the data frame is always an even number.
