Why isn’t the 1553 board sending all the BC messages that I have specified in the frame?

There is not enough time in your frame for the messages you are asking the board to send. Our board does not send messages that exceed the frame time. This causes you to miss messages when you observe the bus with the bus analyzer.

Keep in mind that 1553 is a 1MHz bus, so it takes one microsecond per bit. Each word consists of a three bit-time sync pattern, 16 data bits, and a parity bit, giving us 20 bits per word. Therefore, each word takes 20 microseconds on the bus. For BCRT and RTBC messages, each message consists of a COMMAND word, STATUS word, and up to 32 DATA words. There is a STATUS RESPONSE time of 4-12 microseconds and an intermessage gap time of a minimum of 4 microseconds. For example, assume that the intermessage gap time is 10 microseconds and that our status response time is 10 microseconds. A 32-word message takes (34 words * 20us/word) + 10us gap + 10us status response, which gives us 700 microseconds to send the message.