If the channel and communications equipment are configured to use Mark Parity, the communications equipment expects the Parity bit to be set to 1 in all data transmissions:
- If the Parity bit is set to 1, the communications equipment will transmit the message to the ‘receiving’ application.
- If the Parity bit is not set to 1, it means that the data has probably been corrupted during transit. The ‘receiving’ communications equipment will disregard the data and will not reply to the message. If ClearSCADA is the ‘sending’ application and it does not receive a reply, it will time out the message. If repeated attempts to send the message continue to time out, ClearSCADA will generate an alarm.
However, in some instances, the ‘receiving’ communications equipment is not expected to reply even if the message was received correctly. In these situations, further diagnostics of the communications network and device are required.