Glitch suppression prevents the USCI from being accidentally started. Any glitch on UCAxRXD shorter than the deglitch time tt (approximately 150 ns) is ignored by the USCI, and further action is initiated as shown in Figure 36-8 (see the device-specific data sheet for parameters).

When a glitch is longer than tt, or a valid start bit occurs on UCAxRXD, the USCI receive operation is started and a majority vote is taken (see Figure 36-9). If the majority vote fails to detect a start bit, the USCI halts character reception.