JPH0523251U - Digital signal output device - Google Patents

Abstract

(57) [Abstract] [Purpose] In a device that outputs a signal by operation from an external system, if an abnormality occurs in the control bus input to the device, a digital signal output with a protection function to prevent malfunction The one that realizes the device. [Structure] A control bus for transmitting settings made in an external system, a means for judging whether or not there is an abnormality in the control bus, a means for detecting whether a signal pattern of the bus is for outputting data, and a data bus. A digital signal output device for a signal output device, comprising means for turning the output on and off and means for generating data for preventing output when there is an abnormality in the control bus.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an output device of a digital signal generator, and more particularly, to a device for directly outputting a test digital signal to a bus of an external system (system under test), when an abnormal state occurs in the output digital signal. The present invention relates to a digital signal output device having a protection function.

[0002]

[Prior Art]

 FIG. 3 shows a block diagram of an output device of a conventional digital signal generator. In the figure, 6 is a signal generating means for outputting a test digital signal to an external system, 3 is a setting means, and the pattern of the output permission signal at the time of outputting the digital signal from the signal generating means 6 is a matching pattern. Is set in the digital signal output device and output to the comparison means 4. The comparison means 4 compares the output permission signal input from the external system with the matching pattern input from the setting means, and outputs a comparison result signal indicating a match / mismatch between the two values to the buffer gate 5. The buffer gate 5 outputs the digital signal from the signal generating means 6 to the data bus of the external system in response to the comparison result signal from the comparing means 4. The operation of the conventional example configured by these will be described. The comparison means 4 compares the signal of the control bus input from the external system with the matching pattern value of the setting means 3, and if both signals match, the digital signal output from the signal generating means 6 is passed through the buffer gate 5. To the digital bus of the external system. (However, the timing for outputting a digital signal to this external system is set by the external system. At this time, the data bus is in the signal receiving state.) If they do not match, set the buffer gate 5 to high impedance and set the external data. Electrically isolate the bus from the signal generator data bus. This control is based on the comparison result signal input from the comparison means 4 to the buffer gate 5. In a device having such a structure, that is, in an output device having an input for performing something by an operation from an external system, the same pattern as the coincidence pattern output by the setting means 3 by mistake due to disconnection of the control bus connection, etc. If something happens (hereinafter referred to as "abnormality"), a digital signal is output to the external system, and the data bus is not in the signal receiving state, so data collision occurs and the external system is destroyed. There is a problem that there is a danger of

[0003]

[Problems to be solved by the device]

 The present invention has been made in order to solve the above problems, and when an abnormality occurs in the control bus, the output is not automatically output, that is, the fail-safe structure prevents the connection of the external system from connecting. It aims to realize a digital signal output device with a protection function.

[0004]

[Means for Solving the Problems]

 The present invention relates to a digital signal output device which outputs a digital signal from a signal generating means directly to a data bus of an external system through a buffer gate based on an operation from the external system, based on an operation signal from the external system. The setting means for setting the pattern of the digital signal to be output to the data bus, the protection pattern setting means for outputting the protection pattern according to the pattern from this setting means, the operation from the external system and the protection pattern are input. If the operation signal is normal, the operation signal is output, and if it is not normal, the judgment means that outputs the protection pattern is compared with the signal input from the judgment means and the matching pattern input from the setting means. And a comparison means for outputting a comparison result signal indicating a match / mismatch between the two values to the buffer gate. A digital signal output device.

[0005]

[Action]

 When an abnormality occurs in the control bus that is input to the digital signal output device of the present invention, a protection pattern for preventing malfunction is input to the comparison device, and the buffer gate is closed (electrically isolated state). Since no digital signal is output to the data bus, it is possible to prevent the external system from being destroyed.

[0006]

【Example】

 FIG. 1 is a block diagram of the present invention. In FIG. 1, the same parts as those in FIG. 3 are designated by the same reference numerals.

Reference numeral 1 is a protection pattern setting means, which generates a protection pattern to be output to the determination means when an abnormality occurs in the control bus based on the matching pattern input from the setting means 3. Reference numeral 2 is a judging means, which inputs the signal generated by the protection pattern setting means 1 and the signal of the control bus, judges whether the control bus is normal, and if normal, compares the signal of the control bus with the comparing means. 4, and when an abnormality occurs, the protection pattern input from the protection pattern setting means is output. Normally, the signal on the control bus is input to the comparing means 4 via the judging means 2. The following operation is the same as that of the conventional example. The comparison means 4 compares the matching pattern input from the setting means 3 with the signal on the control bus and outputs it to the buffer gate 5 as a comparison result signal. The comparison result signal indicates the match / mismatch of the two signals input to the comparison means 4. If they match, the buffer gate 5 is opened, and the digital signal is output from the signal generating means to the data bus of the external system. If they do not match, the buffer gate 5 is electrically isolated. The protection pattern setting means 1 outputs a protection pattern different from the matching pattern in all cases. Therefore, when an abnormality occurs in the control bus, the comparison means 4 compares the protection pattern through the determination means 2 with the matching pattern, so that the comparison result signal always indicates that the output signals do not match. .. Therefore, the data will not be erroneously output to the data bus of the external system without opening the buffer gate 5.

FIG. 2 shows a 1-bit circuit diagram of an embodiment of a portion that performs the protection function of the present invention. In FIG. 2, 11 is an inverter for inverting the output from the setting means 3, 12 is a pull-up / pull-down resistor for fixing the output of the inverter 11 when the control bus is in a floating state, and 13 is a control bus. Is a buffer with an infinite input impedance so that the input value can be output to the comparison means 4 when the signal is input. In the circuit configured by these, when a certain bit of the control bus is in a floating state, the value of the corresponding bit is inverted and input to the comparison means 4 in the matching pattern, so that the comparison output from the comparison means 4 is performed. The result signal always indicates that the signals being compared do not match. Therefore, the buffer gate 5 does not open and data is not accidentally output to the data bus of the external system.

[0009]

[Effect of the device]

 As described in detail above, according to the present invention, by providing the protection function composed of the inverter, the pull-up / pull-down resistor and the buffer, the data of the external system can be stored when the control bus is abnormal. It is possible to realize a digital signal output device that does not output a digital signal to the bus and prevents destruction of the external system.

[Brief description of drawings]

FIG. 1 is a block diagram of the present invention.

FIG. 2 is a circuit diagram of an embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Protection pattern setting means, 2 ... Judgment means, 3 ... Setting means, 4 ... Comparison means, 5 ... Buffer gate, 6 ... Signal generating means, 11 ... Inverter, 12 ... Pull-up / pull-down resistance, 13 ... Buffer.

Claims (1)

[Scope of utility model registration request] 1. A digital signal output device for directly outputting a digital signal from a signal generating means to a data bus of an external system via a buffer gate based on an operation from the external system, and outputting the data based on the operation from the external system. Setting means for setting the pattern of the digital signal to be output to the bus, protection pattern setting means for outputting the protection pattern according to the pattern from this setting means, and input the operation signal and the protection pattern from the external system, If the operation signal is normal, the operation means outputs an operation signal, and if it is not normal, the judgment means for outputting the protection pattern is compared with the signal inputted from the judgment means and the matching pattern value inputted from the setting means, And a comparison means for outputting a comparison result signal indicating a match / mismatch between the two values to the buffer gate. Digital signal output device.