I can not find any information about how the I/O setting for DIO1 - UART DATA Indicator works. I connected an LED to the pin (TH - 19) and it seems not to be obvious as to how this pin works in this mode. I am using the 900HP S3B as an Indirect Message Poller, with Assync. Cyclic Sleep Pin Wake. I would like to use the UART Data present indicator to indicate (interrupt) the host that there is data present rather than have to wake and wait a period every poll to see if data is presented to the Serial buffer. Any insight would be appreciated, is there a document?