| 摘要 |
A multipoint communications system for transmitting the values of a multiplicity of analog parameters from one point digitally to another point and reconverting then into analog parameters. The system includes a plurality of input modules which communicate with respective output modules over a communications link. The input and output modules are configured similarly with a control processor connected to either multiplexing circuitry, in the case of an input module, or demultiplexing circuitry in the case of an output module. The multiplexing circuitry is connected to a plurality of configurable input circuits which receive the values of the various measured conditions or parameters. The demultiplexing circuitry is connected to a plurality of configurable output circuits which output the values of the various measured conditions or parameters. In a preferred protocol, a link master is chosen from among the input modules to generate a polling sequence for the input-output module pairs. A poll of a particular module is taken by generating a wake-up message, which the module responds to with a ready message. When a ready message is received, the link master generates a go-ahead signal and becomes dormant for a time period before continuing. Otherwise, if a ready message is not received, the poll will continue. When a module has authority to communicate, it wakesup its corresponding output module, which responds with a ready message. When the selected input module receives a ready message, it transmits a plurality of stored digital values corresponding to the analog parameters which were input. The system includes a communications mode where the values are transmitted, a calibration mode where the range of input and output values are set for each module, a configuration mode where each module is assigned an address and each input and output matched and configured. An input can be configured for voltage, current, TTL, or contact closure inputs and an output configured to output voltage, current, TTL, or contact closure. |
