SWRU626 December 2025 CC3501E , CC3551E
The PDM module can accept a Manchester‑encoded bitstream. The format is selected using PDM.CCTL register. The decoder requires a zero‑to‑one or one‑to‑zero transition to lock.
In Manchester Input Mode, the oversampling ratio is fixed at 16 and the input data will be synchronized. The first transition could be ignored due to synchronization overhead and on the following transition/second transition, counter is started to count pulses between samples and total samples. Counter on every new sample should be between a fixed window. A variable window can be designed to accommodate initial variations and reduce window size as sample count goes up. Initial sequence is planned to be back to back opposite values. After “X” transitions if the window is not violated, status is issued and data decoding starts. Till then output data and clock are 0. A new sample triggers clock edge and another new sample within window limit or 3/4th clock pulse width would result in edge switch. The window comparison is done during clock generation and the Data_out is same as Data_in, according to IEEE standard.