Title :
Biodirectional RS 232/422 communications over two wires including DC power lines
Author :
Murray, T., Jr. ; Chism, A. ; Steutermann, Ed
Author_Institution :
Dept. of Electr. Eng., Louisville Univ., KY, USA
Abstract :
A communications/control system that can utilize most any two-wire communications system that is already installed in a large building is described. Some of the important design issues for utilizing existing two-wire communications systems for controlling multiple positioner control units connected to the same two wires are presented. Because of the uncertain distances, most over 100 ft, and RS422A transmitting/receiving unit is used as the serial interface. Multiple positioners can be controlled over a two-wire dedicated system using an IBM XT/AT compatible computer as the host controller. Thus, the receiving circuits and the software are designed so that all units receive the serial control data but only the addressed unit responds. When the designated module receives the serial information, a confirmation signal is transmitted to the computer confirming that the data have been received, and the process is halted. If the computer does not receive a confirmation signal, it sends the information again and alerts the user of a possible problem
Keywords :
IBM compatible machines; carrier transmission on power lines; computer interfaces; telecommunication systems; telecommunications computer control; DC power lines; IBM AT; IBM XT; IBM compatible computer; RS232; RS422A transmitting/receiving unit; building; communications system; confirmation signal; control system; host controller; multiple positioner control units; receiving circuits; serial control data; serial interface; software; two-wire communications system; Actuators; Application software; Buildings; Circuits; Communication system control; Control systems; Instruments; Software design; Switches; Wires;
Conference_Titel :
Southeastcon '90. Proceedings., IEEE
Conference_Location :
New Orleans, LA
DOI :
10.1109/SECON.1990.117764
