I've been struggling with a TSS463B VAN Datalink Controller and I'm not able to decrypt its datasheet. I'm using SPI to interface the controller (basically following this: https://github.com/lazarov-g/vanreader ) but could not find a reliable way to detect when a new message arrives. I can see that there is a Last Message Status Register which holds the channel number that was successfully transmitted or received, but it's a read only register, so I can't set it after reading out the contents of the corresponding mailbox. Maybe there is another way, but I couldn't figure it out. And also cannot figure out how to send a message, if I understand it correctly, I need to set the corresponding channel registers as seen on page 37 and 44, or am I wrong? Any help is greatly appreciated.