AJA Ki Pro Ultra Machine Control Manual page 8

the CONTROLLER detects a communication error, and must execute an
appropriate process.
5. When the DEVICE detects a communication error, it must immediately
transmit a NAK to the CONTROLLER. (The contents of an error is shown on
the COMMAND tables.) When the CONTROLLER receives a NAK, it must
immediately stop transmission of the COMMAND block. The DEVICE must
not accept a subsequent command within 10 milliseconds after that (except
NAK-UNDEFINED command) and must execute a necessary process.
Ki Pro Ultra Products Machine Control Guide v3.0 8 www.aja.com