The use of serial digital transmission by supervisory control and data acquisition (SCADA) systems having geographically dispersed terminals is addressed. These types of systems typically utilize dedicated communication channels, such as private microwave channels or leased telephone lines, which are limited to data rates of less than 10 000 bits/s. Wideband local networks used for high-speed data acquisition and control functions are excluded. This standard covers the communication channels, channel interfaces, message format, information field usage, and communication management. A standard message protocol is defined to the octet level, rather than to the bit level; most details at the bit level are left to the manufacturers of SCADA equipment to define and implement. |