I'm trying to write to the SPI FIFOWR register setting the lower 16 bits only (data to be shifted out). The UM claims that this register can be accessed for data writes only (not updating configuration) and that halfword writes to the lower 16 bits or word writes with the upper 16 bits all zeros will result in preservation of the original configuration. I have tried both methods as well as 16 bit DMA transfers and the configuration appears to be lost in all cases. I verified that the generated assembly is what I expect. The SPI peripheral is configured for 16bit transfers.
Has anyone experienced this or been able to write data only to this register?