The TPI physical layer operates synchronously on the TPICLK provided by the external programmer. The dependency between the clock edges and data sampling or data change is shown in the figure below. Data is changed at falling edges and sampled at rising edges.
Figure 1. Data changing and Data
sampling.
The TPI physical layer supports two modes of operation: Transmit and Receive. By default, the layer is in Receive mode, waiting for a start bit. The mode of operation is controlled by the access layer.