SLASEC8B February 2017 – January 2019 PGA460-Q1
A checksum field is transmitted as the last field of every UART frame. The checksum contains the value of the inverted byte sum with carry operation over all data fields and the command field (command field for master only). On a master-to-PGA460-Q1 transmission, the checksum field is calculated by the master device and checked by the PGA460-Q1 device. On a PGA460-Q1-to-master transmission, the PGA460-Q1 device generates the checksum and the master validates the integrity. The format of the checksum is identical to the data field and the procedure for calculating the checksum is explained in the Time-Command Interface section. Because the UART interface is a byte-based interface, no zero padding occurs in the process of calculating the checksum.
When the master device calculates the checksum field, the calculation occurs on the UART command field followed by all UART data fields that are transmitted as a part of the current communication frame. When the PGA460-Q1 device is calculating the checksum field, the calculation includes the diagnostic data field (see the Diagnostic Field section) followed by all UART data fields in the current frame. The sync field (0x55) is not included as part of the checksum calculation.