JPS6411434A - Data transmission equipment - Google Patents

Abstract

PURPOSE:To instantaneously judge trouble occurrence on a master station side and to prevent ineffective data transmission from being performed by providing a sent clock generating circuit on a slave station side and sending and abnormality information frame to a master station in synchronizingly with a clock generated by said circuit. CONSTITUTION:When a slave station receives no clock owing to trouble occurrence, a received clock break detecting circuit 12 detects a clock break and supplies detection signals 26 and 27 to a sent clock switching circuit 14 and a sent data switching circuit 15. The circuit 14 switches the selection of a sent clock from a sent-back clock circuit 17 to the sent clock generating circuit 16. At this time, the circuit 16 generates the sent clock 28 of the same frequency with a clock received in a normal state. Further, the circuit 15 switches the selection of sent data from a transmission circuit 18 to an abnormality information frame generating circuit 19. At this time, the circuit 19 generates the abnormality information clock 29. This frame 29 is sent to the master station through a transmission line 11 by using the clock 28.