The MAX3140 supports a common multidrop communication technique referred to as 9-bit mode. In this mode, the parity bit is set to indicate a message that contains a header with a destination address. Set the MAX3140’s parity mask to generate interrupts for this condition. Operating a network in this mode reduces the processing overhead of all nodes by enabling the slave controllers to ignore most message traffic. This relieves the remote processor to handle more useful tasks.In 9-bit mode, the MAX3140 is set up with eight bits plus parity. The parity bit in all normal messages is clear, but is set in an address-type message. The MAX3140’s parity-interrupt mask generates an interrupton high parity when enabled. When the master sends an address message with the parity bit set, all MAX3140 nodes issue an interrupt. All nodes then retrieve the received byte to compare to their assigned address. Once addressed, the node continues to process each received byte. If the node was not addressed, it ignores all message traffic until a new address is sent out by the master.The parity/9th-bit interrupt is controlled only by the data in the receive register and is not affected by data in the FIFO, so the most effective use of the parity/9th-bitinterrupt is with FIFO disabled. With the FIFO disabled, received non-address words are ignored and not even read from the UART.