JPH09282062A - Interface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a remarkable noise, which can not be completely removed, and to deal with this noise without resetting an entire system by discriminating the signal state of a signal line after the noise is removed by a noise removing circuit, and instructing the execution of noise countermeasure processing when that state is not normal. SOLUTION: Signal lines 110 and 111 dedicated to noise detection are provided in a signal cable 3 and noise removing circuits 101 and 103 are installed. Comparators 102 and 104 respectively compare signal potentials on the signal lines 110 and 111 after noise removing processing with a threshold value settled within a normal range and detect communication abnormality generated on signal lines L0-L7 for data transfer. Corresponding to the input of this abnormality detecting signal, a D flip-flop 102 generates an interrupting signal XIRQ for instructing the noise countermeasure processing to the CPU of a printer 2. When this signal XIRQ is inputted, the CPU decides that noise removal is not completely executed, and performs the predetermined countermeasure processing concerning noise mixture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallel computer connected between a host computer and a peripheral device such as a printer.
The present invention relates to an interface suitable for an unbalanced type interface.

[0002]

2. Description of the Related Art A typical noise elimination circuit of a conventional balanced type interface is shown in FIG. In the system (a) of FIG. 1, the driver of the host computer 1 and the receiver of the printer 2 are connected by an interface, that is, a signal cable 3. The signal cable 3 has a signal line for data transfer and a return line, and a resistor r1 is provided between the signal line and the return line. In the system of reference numeral (b) of FIG. 1, a low-pass filter composed of a resistor and a capacitor is provided on each of the signal line and the return line.

A conventional unbalanced interface is shown in FIG. In FIG. 2, the transmission circuit 10 of the host computer 1 includes a driver (transmission element) 4 connected to the CPU bus (signal lines d0 to d7) and a pull-up resistor 5. The receiving circuit 20 of the printer 2 includes a pull-up resistor 6, a low-pass filter resistor 7, a low-pass filter capacitor 8, and a receiver (reception element) 9. The structure of the low-pass filter is shown in FIG. The data received by the receiving circuit 20 is the CPU bus (signal line d0
Through d7), the data is transferred to a CPU (not shown) that controls printing.

The power supply monitoring device 21 resets the entire system of the printer when the power is turned on, and resets the entire system when an abnormal voltage of the signal cable 3 is detected. The signal cable 3 connecting between the transmission circuit 10 and the reception circuit 20 has a signal line for data transfer, a braided wire for grounding, and a grounding wire, and the outside is shielded.

[0005]

The superposition of noise on the signal line in the unbalanced interface according to the present invention will be described. The noise that has flown into the signal line cable 3, that is, radiated noise, reaches the grounding braided wire, the grounding wire, and the signal lines L0 to L7 for data transfer, but the noise reaches because the grounding impedance of the grounding wire braided wire is low. However, it is immediately absorbed. However, the flying noise passes through the braided wire and is mixed into the data transfer signal lines (hereinafter simply referred to as signal lines) L1 to L7 having a high ground impedance. The mixing point is indicated as in in FIG. FIG. 4 shows a noise mixing waveform when the potential of the signal line is low (Lo), and FIG. 5 shows a noise mixing waveform when the potential of the signal line is high (Hi). This noise waveform is charged and discharged in the low-pass filter of the printer 2 according to the characteristics shown in FIG. 6, and the noise waveform is removed.

When the noise length is smaller than the time constant of the low-pass filter, the noise waveform is removed, but when it is larger than the time constant t shown in FIGS. 7 and 8, that is, the threshold VHmin in FIG. When the noise waveform exceeds the threshold value VLmin of 5, the low-pass filter cannot completely remove the noise waveform, and a part of the noise is transferred to the receiver 9. The power supply voltage monitoring device 21 outputs an interrupt signal Xreset to the CPU when detecting a voltage abnormality in the data transfer signal line. In response to this, the CPU operates and resets the entire system. As a result, there is a problem that various parameters for print processing stored in the memory and data received from the host computer 1 so far are lost.

Therefore, an object of the present invention is to provide an interface capable of detecting a large amount of noise that cannot be completely removed, and dealing with this noise without resetting the entire system.

[0008]

In order to achieve such an object, the invention of claim 1 connects a transmission circuit of a first device and a reception circuit of a second device with a signal line. In the interface for removing the noise mixed in the signal line by the noise removing circuit, the noise handling processing on the second device side when the noise is mixed is determined in advance, and after the noise removing circuit removes the noise. It is characterized by further comprising: determination means for determining whether or not the signal state of the signal line is normal, and instructing means for instructing execution of the noise countermeasure process when a negative determination is obtained.

According to a second aspect of the present invention, in the interface according to the first aspect, the judging means is a signal line separate from the signal line, and the transmitting circuit of the first device and the second device. A signal line connecting between the receiving circuit and the receiving circuit, a noise removing circuit for removing noise mixed in the signal line, and a signal voltage after the noise removing process of the noise removing circuit are compared with a threshold value that defines a normal range. And determining whether the signal state of the signal line after being removed by the noise removal circuit is normal based on the comparison result of the comparator.

According to a third aspect of the present invention, in the interface according to the second aspect, the separate signal line is used exclusively for detecting the noise.

According to a fourth aspect of the present invention, in the interface according to the second aspect, the two separate signal lines are used, one of them is used for detecting + polarity noise, and the other one is used. Is used for the detection of polar noise.

According to a fifth aspect of the present invention, in the interface according to the first aspect, the determination means is a signal line separate from the signal line, and the transmission circuit of the first device and the second device. And a comparator for comparing the level of noise mixed in the signal line with a range determined to be normal, and removed by the noise removal circuit according to the comparison result of the comparator. It is characterized in that it is determined whether or not the signal state of the signal line after being processed is normal.

According to a sixth aspect of the present invention, in the interface according to the fifth aspect, the number of the separate signal lines is one, and the noise mixed in the separate signal lines is amplified by a transformer.
The amplified noise is compared by a rectifier.

According to a seventh aspect of the invention, in the interface according to the first aspect, the noise coping process is a process for requesting the first device to retransmit.

According to an eighth aspect of the present invention, in the interface according to the first aspect, the noise coping process is a resetting process of a specific parameter used by the second device.

According to a ninth aspect of the present invention, in the interface according to the first aspect, abnormality detecting means for detecting a voltage abnormality of the signal line and resetting of the entire second device when the voltage abnormality is detected. And a reset instruction means for instructing.

According to a tenth aspect of the present invention, when both the instruction of the instruction means according to the first aspect and the instruction of the reset instruction means according to the ninth aspect occur, processing for instructing the reset instruction is executed. Instead, the process instructed by the instructing means is executed.

According to an eleventh aspect of the invention, in the interface according to the first aspect, the first device is a host computer and the second device is a printer.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 3 shows the structure of an interface to which the present invention is applied. The same parts as those of the conventional example shown in FIG.

The circuits related to the data transfer signal lines of the transmission circuit 10 of the host computer 1 and the reception circuit 20 of the printer 2 can be the same as the conventional ones. In the present embodiment, it is determined whether or not there is an abnormality in the data signal after noise removal, and if an abnormality determination is obtained, the CPU of the printer 2 resets various parameters as abnormality processing.

Therefore, the signal line 1 dedicated to noise detection is used.
10 and 111 are provided in the signal cable 3. Since the unbalanced interface normally has an empty signal line in the signal cable 3, the signal line s (+), s
Use (-). The signal line 110 is a signal line for detecting noise whose potential drops (denoted by −). Signal line 1
Reference numeral 11 is a signal line for detecting noise (indicated as +) whose potential rises. The same noise removal circuits 101 and 103 as the noise removal circuit (low-pass filter) installed on the data signal lines are installed on the signal lines 110 and 111.

The comparator 102 cannot completely remove the signal potential after noise removal processing on the signal line 110 by comparing it with a threshold value which defines a normal range, and the signal potential after noise removal becomes smaller than the threshold value-noise, That is, the communication abnormality that occurs when the data transfer signal lines L0 to L7 are at the low level is detected. The comparator 104 cannot completely remove the signal potential after noise removal processing on the signal line 111 by comparing it with a threshold value that defines a normal range, and the signal potential after noise removal becomes larger than the threshold value + noise, that is, A communication abnormality that occurs when the data transfer signal lines L0 to L7 are at a high level is detected. When the above communication abnormality is detected, the comparator 1
A high level abnormality detection signal is input to the D-type flip-flop 106 from 02 and 104 through an OR gate. In response to the input of this abnormality detection signal, the D-type flip-flop 106 generates an interrupt signal XIRQ for instructing the CPU of the printer 2 to perform noise countermeasure processing. In this embodiment, as in the conventional case, when the power supply voltage monitoring device 21 detects a voltage abnormality of the data signal line in order to instruct the reset of the entire system, the interrupt signal Xreset is output to the CPU.

When either of the interrupt signals Xreset or XIRQ is generated, the CPU executes the processing procedure shown in FIG. When the CPU inputs the interrupt signal Xreset to the first interrupt terminal, the interrupt signal XIR
It is determined whether or not Q is input to the second input terminal (step S1 in FIG. 10).

If an affirmative determination is obtained here, it is determined that the noise removal has not been completely performed, and the CPU executes a process for coping with noise mixing (step S2). In this embodiment, a message requesting retransmission of data is transmitted to the host computer 1 on the data transmitting side.
Further, the parameters used on the printer side which are set in advance are reset (step S2).

On the other hand, if it is determined in step S1 that the interrupt signal IRQ is not generated, it is determined that not the noise is mixed but the voltage abnormality related to the entire system, and the reset (initialization process) of the entire device is executed as in the conventional case. Yes (step S3).

When the interrupt signal Xreset signal is not generated and only the interrupt signal XIRQ is generated, the noise coping process of step S2 is executed.

As described above, in the present embodiment, it is possible to detect the situation where the noise removal is not completely performed.
Recovery processing related to communication errors may be performed without resetting the entire system.

FIG. 11 shows the system configuration of the second embodiment. In the second embodiment, the signal line 11 for detecting the mixing of noise
There is only one, and the transformer 200 and the rectifier 201 are connected to the signal line 111. In this configuration, noise mixed in the signal line 111 is amplified by n times on the secondary side L2 of the transformer 200, and then rectified by the rectifier 201. As a result, a voltage of positive polarity is generated regardless of the polarity (+/−) of noise, so that the flip-flop 102 is detected when the comparator 202 detects a voltage higher than a threshold value determined to be normal for the data transfer signal lines L0 to L7. Generates an interrupt signal XIRQ.

This example has the advantage that only one signal line is required. It goes without saying that the CPU has the power supply voltage monitoring device 21 and the CPU executes the processing procedure of FIG. 9.

[0030]

As described above, according to the first aspect of the present invention, it is possible to detect that noise removal has not been completely performed, and therefore it is possible to deal with an error caused by the resetting without resetting the entire system.

According to the second, third, and fifth aspects of the present invention, by installing a signal line for noise detection that is not used for data communication, it is possible to reliably detect the mixed noise and the noise removal state.

According to the invention of claim 4, noise of both + and − polarities can be detected.

According to the sixth aspect of the present invention, it is possible to detect noise of both + and − polarities with one signal line for noise detection.

According to the invention of claim 7, correct data can be received with respect to the data destroyed by noise.

According to the eighth aspect of the invention, it is possible to restore the correct parameter change due to the data destroyed by noise.

According to the invention of claim 9, not only the communication abnormality due to noise but also the communication abnormality such as general voltage abnormality including noise can be detected.

According to the tenth aspect of the invention, the general voltage abnormality and the communication abnormality due to noise can be discriminated.

According to the eleventh aspect of the present invention, it is possible to prevent malfunction of a printer having a large amount of communication data, reduce printing failures, and enhance economic effects.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a system configuration of a balanced type conventional example.

FIG. 2 is a circuit diagram showing a system configuration of an unbalanced conventional example.

FIG. 3 is a circuit diagram showing an example of a low-pass filter.

FIG. 4 is a waveform diagram showing a signal waveform in which noise is mixed.

FIG. 5 is a waveform diagram showing a signal waveform in which noise is mixed.

FIG. 6 is an explanatory diagram showing characteristics of a low-pass filter.

FIG. 7 is an explanatory diagram showing characteristics of a low-pass filter.

FIG. 8 is an explanatory diagram showing characteristics of a low-pass filter.

FIG. 9 is a circuit diagram showing a system configuration of the present embodiment.

FIG. 10 is a flowchart showing the contents of data recovery processing after abnormality detection.

FIG. 11 is a circuit diagram showing a system configuration of a second embodiment.

[Explanation of symbols]

 1 host computer 2 printer 3 signal cable 10 transmitter circuit 20 receiver circuit

Claims (11)

[Claims] 1. An interface in which noise is mixed in an interface in which a transmitting circuit of a first device and a receiving circuit of a second device are connected by a signal line, and noise mixed in the signal line is removed by a noise removing circuit. And a determination means for determining whether or not the signal state of the signal line after being removed by the noise removal circuit is normal in advance, An interface comprising: an instruction means for instructing execution of the noise coping processing when a determination is obtained. 2. The interface according to claim 1, wherein the determination means is a signal line separate from the signal line, and the determination circuit is a transmission circuit of the first device and a reception circuit of the second device. A signal line connecting between the signal lines, a noise removing circuit for removing noise mixed in the signal line, and a comparator for comparing the signal voltage after the noise removing process of the noise removing circuit with a threshold value defining a normal range An interface characterized by determining whether or not the signal state of the signal line after being removed by the noise removal circuit is normal based on the comparison result of the comparator. 3. The interface according to claim 2, wherein the separate signal line is exclusively used for detecting the noise. 4. The interface according to claim 2, wherein the number of the separate signal lines is two, one of which is used for detection of positive polarity noise, and the other one of which is negative polarity noise. An interface characterized by being used for detection of. 5. The interface according to claim 1, wherein the determination unit is a signal line separate from the signal line, and the determination circuit is a transmission circuit of the first device and a reception circuit of the second device. A signal line connecting between the signal line and a comparator for comparing with a range in which the level of noise mixed in the signal line is determined to be normal, and the comparator after being removed by the noise removing circuit according to the comparison result of the comparator An interface characterized by determining whether or not the signal state of a signal line is normal. 6. The interface according to claim 5, wherein the number of the separate signal lines is one, the noise mixed in the separate signal lines is amplified by a transformer, and the amplified noise is compared by a rectifier. Interface characterized by. 7. The interface according to claim 1, wherein the noise coping process is a process of requesting retransmission of the first device. 8. The interface according to claim 1, wherein the noise coping process is a process of resetting a specific parameter used by the second device. 9. The interface according to claim 1, further comprising an abnormality detecting unit that detects an abnormality in the voltage of the signal line,
An interface further comprising reset instruction means for instructing reset of the entire second device when the voltage abnormality is detected. 10. The instruction of the instruction means according to claim 1,
When the instruction of the reset instruction means according to claim 9 is also generated, the processing instructing the reset instruction is not executed,
An interface for executing a process instructed by the instructing means. 11. The interface according to claim 1, wherein the first device is a host computer,
An interface characterized in that the second device is a printer.