SLASEC8B February 2017 – January 2019 PGA460-Q1
The sync field is the first field in every frame that is transmitted by the master. The sync field is used by the PGA460-Q1 device to confirm the correct baud rate of the frame that is send by the master device. This bit width is used to accurately receive all subsequent fields transmitted by the master. The bit width is defined as the number of internal oscillator clock periods that make up an entire bit of data transmitted by the master. This bit width is measured by counting the number of slave oscillator clocks in the entire length of the sync field data, and then dividing by 8. Figure 23 shows the format of the sync field.
Consecutive sync-field bits are measured, including the start and stop bits, and compared to determine if a valid sync field is being transmitted to the PGA460-Q1 device is valid. If the difference in bit widths of any two consecutive sync field bits is greater than ±25%, then the PGA460-Q1 device ignores the rest of the UART frame; essentially, the PGA460-Q1 device does not respond to the UART message.