Transmit operates in three modes: Immediate FIFO, Trigger FIFO and SCHEDULED. Schedule mode transmits ARINC data words according to a user pre-built schedule in Schedule Memory. There are various Schedule Transmit library commands that define how messages are sent from Tx Schedule Memory, for example how many messages to be sent, jumping to other address locations within schedule memory, the gap time, and how to trigger transmission, so there are various possible ways to set up a schedule. In the naibrd SSK (Software Support Kit located on our website) we have Arinc Transmit sample to indicate the methods to call in the naibrd library to configure the ARINC channel to transmit ARINC messages in FIFO or scheduled mode. This sample code in addition to the AR1 information located in the Operations Manual should provide you with enough information to calculate a schedule. The ARINC message is always 32-bit time. The gap or fixed-gap time is whatever you set it to (minimum gap time between messages is 4-bits).