JPS6449344A - Loop back control system - Google Patents

Abstract

PURPOSE:To simply attain control to execute loop back only with a specified receiving station from any station by providing a control data inserting means to insert a node number to designate a control code to set or cancel loop back control and a receiving point in which the loop back control is executed to transmitting data and a first node number detecting means to detect whether the node number of receiving data is zero or not. CONSTITUTION:Data I transmitted from a front step are inputted by a buffer 1 and converted to parallel data by a shift register 2. The inputted data converted to parallel data by the shift register 2 are inputted to comparing circuits 3 and 4, a decrement circuit 5 and a gate circuit 8. In the comparing circuit 4, whether the control code of the inputted data is coincident with control data given in advance or not is compared and when they are not coincident, an output terminal A=B is made low level. When the control code is coincident with the control data, the output terminal A=B is made high level and an enable terminal E of the decrement circuit 5 is turned on. Then, this circuit is operated. The decrement circuit 5 subtracts 1 from an inputted node number and outputs the result to a comparing circuit 6 and a gate circuit 7.