Question: What is the purpose of the IN_DATA action in the GPIF state machine?
The IN_DATA action samples data from the data bus and moves to the destination specified. The destination can be the DMA channel or the firmware application. See the firmware API, CyU3PGpifReadDataWords(). Note that the option for selecting the destination thread is available only when the destination is the DMA channel with the addressing mode as Thread selected by the state machine (number of address lines = 0).