JPH0454746A - Communication equipment - Google Patents

Abstract

PURPOSE:To always maintain the bypass operation by adopting the constitution of the communication equipment such that a bypass means sends a serial communication signal independently of the state of reset even when a slave communication equipment is reset. CONSTITUTION:A slave communication equipment 1 not only sends a serial signal from a master communication equipment received by an input buffer 9 to a serial parallel conversion section 2 but also bypasses output buffers 4, 5 to send the serial signal from the said master communication equipment to other slave communication equipment. Moreover, a serial return signal from the other slave communication equipment inputted from input buffers 6,7 and a serial return signal from a parallel serial conversion section 3 are synthesized by an OR circuit 11 to bypass the serial return signal from the other slave communication equipment. Moreover, the bypass operation is always maintained by the output buffers 4, 5, 10 independently of the presence of a state when a reset signal is given to slave communication equipments.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a communication device that controls information exchange within the device necessary for operating the device, for example, in a device such as a laser beam printer. be.

[Prior Art] Conventionally, when controlling the operation of a device by using serial communication to exchange information between a central processing unit that performs main control of the device and each unit scattered within the device, the system shown in FIG. It was configured and connected as follows.

In FIG. 5, MASTER 50 is located within the central processing unit and is a main communication device that controls serial communication. Further, SLA VE 51, 52, 53, and 54 are communication devices located in each unit scattered within the device, and receive serial communication and execute information exchange.

Since this serial communication is carried out on an l:N basis, information exchange of serial data signals is configured such that the main communication device and each communication device are independently connected in parallel.

[If the problem you are trying to invent or solve] However,
In the conventional example described above, the serial data signal line wired from the main communication device is connected in parallel even within the device, so the wire length is long, which may cause malfunction due to the influence of noise generated within the device. Furthermore, in order to increase the drive capability of the master communication device, some kind of drive means is required, which increases the cost.

In addition, for units that can be attached and detached by the user, external noise may be directly transmitted to the serial data signal line due to electrostatic noise from the connector that is the cut point when attaching or detaching, which may damage the main control unit. There was also the drawback that service and maintenance costs were too high.

Furthermore, if there is an error within the device, it may be necessary to forcibly reset the state communication device depending on the unit and turn off all actuators hanging from the state communication device, or depending on the unit, there may be a problem handling process. It may be necessary to continue serial communication for this reason. Therefore, it was necessary to configure the main communication device and each type of communication device to be connected independently and in parallel. - Let's take a laser beam printer as an example. If a jam occurs during paper feeding, it is necessary to immediately stop the high-voltage power output to protect the photosensitive drum and the like. However, when controlling the paper feed unit, if paper feeding is interrupted before the paper feeding logic ends after paper feeding is started, if it is restarted after paper jam processing is completed,
This results in incomplete paper feeding and jams occur again.

[Means for Solving the Problems] According to the present invention, a transmission means (
Hereinafter, it will be abbreviated as bypass means. ), and by providing means that enables the bypass means to transmit serial communication signals regardless of the reset state even if the state communication device is reset, the slave communication device can communicate with the master communication device. This allows the connections within the device to be physically connected from a parallel connection relationship to a series connection relationship, while at the same time maintaining the electrical connection relationship in a parallel connection form. In other words, the master communication device is physically connected to one slave communication device, and each slave communication device is connected in series downstream of that slave communication device (see Figure 3). However, even if the slave communication device that is the most downstream slave communication device in the connection and is in the middle is reset, serial communication can continue without interruption.

[First Example] First, the communication form in the example will be briefly described. The central processing unit has a main communication device (hereinafter referred to as 1) that controls communication.
There are 11v star communication devices (hereinafter abbreviated as slave communication devices), and there are state communication devices (hereinafter abbreviated as slave communication devices) in each unit scattered within the device. Basically, the slave communication device of each unit converts the serial data sent from the master communication device from serial to parallel, and controls switching of actuators in the unit, high voltage power supply, etc. Further, the slave communication device performs parallel-to-serial conversion on information indicating device states distributed in each unit, such as sensor and switch states present in the unit, and feeds it back to the master communication device as serial data.

Note that this serial data signal may have, for example, modulated content.

In other words, the master communication device and slave communication device are 1:
This is l:N communication, which is based on an l handshake, in which a master communication device instructs a slave communication device with which it wants to communicate serial data and executes the communication.

Here, I will explain the actual operation of the slave communication device in a little more detail.

Each slave communication device develops the received serial data input according to predetermined conditions and determines whether the serial signal is issued to itself. If it determines that the serial signal is for itself based on the identification code, etc., it converts the control signal in the received serial data into parallel data.

Further, the slave communication device serializes the parallel input data according to predetermined conditions, and returns a serial signal to the master communication device along with its own device identification code. Also, if there is an instruction to another slave communication device, the slave communication device will not take in the control signal in the received serial data, nor will it return the parallel input data of the slave communication device to the master communication device. .

In this way, serial data collisions are avoided even in handshake-based l:N communication.

The configuration of each unit of this embodiment is shown in FIG. 1, where l is a slave communication device, 17 is an actuator, 18 is a sensor,
19 is a CPU (central processing unit).

The CPU 19 controls the actuator 17 based on the command received from the central processing unit by the slave communication device 1, and also transmits the detection output of the sensor 18 to the central processing unit by the slave communication device 1.

Next, this example will be explained using FIG. 2.

In FIG. 2, l is a block diagram showing a slave communication device, which is a one-chip IC (integrated circuit).

2 is a serial-to-parallel converter that processes the received signal;
It receives the serial signal of the above-mentioned communication form from the master communication device, and outputs the received control output data information to the parallel output 12 to the CPU 19.

3 is a parallel-to-serial converter that processes the transmission signal;
This is where the serial signal in the communication format described above is sent back to the master communication device, and the CPU 19 sends the serial signal back to the master communication device.
The status data information input via 3 is returned.

6 to 9 are input buffers, and 4, 5, and 10 are output buffers. 11 is an OR circuit.

In FIG. 2, the slave communication device l has an input buffer 9
Not only is the serial signal received from the master communication device transmitted to the serial-to-parallel converter 2, but also the serial signal from the master communication device is transmitted to other slave communication devices by bypassing it to the output buffer 4.5. can be transmitted.

Furthermore, input data 6. The OR circuit 11 combines the serial reply signals from other slave communication devices and the serial reply signals from the parallel-serial converter 3 that are input from the interface, thereby bypassing the serial reply signals from other slave communication devices as well. .

Moreover, these output buffers 4, 5, and 10 always maintain a bypass function regardless of whether or not there is a reset signal state for the slave communication device.

Next, an example of the connection between the slave communication device and the master communication device of the present invention will be explained using FIG.

Figure 3 shows one wiring example. In Figure 3, 20 is
It is the master communication device mentioned above, and 21.22, 23.
24 is a slave communication device, and as shown in Figure 0, the serial communication line is scattered in each unit in the device.
Unlike the case shown in the figure, the signal is bypassed from a nearby slave communication device without being routed from the master communication device 20. In addition, even if one slave communication device IC is reset due to a unit abnormality, the serial communication line does not need to be opened, so even if there is a slave communication device that follows the slave communication device IC shown in FIG. As shown in the figure, the operation is equivalent to that of being directly connected to the master communication device.

[Second Embodiment] A second embodiment will be described in FIG. Note that the same reference numerals are used for the same items. In the second embodiment, the slave communication device does not bypass the serial reception signal from the master communication device.

In other words, in the first embodiment as well, the serial reception signal may be bypassed by using a buffer stage, so if necessary, it may be driven using a transistor or the like externally attached to the slave communication device.

It should be noted that the serial bypass circuits shown in the first embodiment and the second embodiment are of a type, and there are no particular limitations as long as the circuits are bypassed and the bypass operation is not interrupted by reset. do not have.

Further, the number of bypasses described in this embodiment is just an example, and is not particularly limited. In other words, there may be one or more than one. Furthermore, it goes without saying that it is not necessary that the number of circuits on the receiving side of the serial signal and the number of circuits on the replying side be the same.

[Effects of the Invention] As explained above, a bypass means is provided for transmitting serial communication signals received and transmitted to the above-mentioned communication device to other communication devices, and even if the above-mentioned communication device is reset, the above-mentioned By providing a bypass means that enables transmission of serial communication signals regardless of the reset state,
The internal connection of the slave communication device to the master communication device is physically connected in a series connection relationship, and at the same time, the electrical connection relationship is maintained in a parallel connection form. Therefore, the serial communication signal trites capability of the master communication device can be maintained as usual, the line length of the serial line and the amount of wire routing can be reduced to a large number, and noise resistance is also improved. Furthermore, compared to configuring the master communication device and each type of communication device to be connected independently and in parallel, this method has the effect of reducing costs by reducing the length, number, and assembly costs of wires. be.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a unit according to a first embodiment of the present invention. FIG. 2 is a block diagram of a slave communication device according to the first embodiment of the present invention. Figure 3 shows #! of the present invention. FIG. 2 is a block diagram showing a connection form of one embodiment. FIG. 4 is a block diagram showing a second embodiment of the present invention. FIG. 5 is a block diagram showing a conventional connection form. 1 is a slave communication device of the present invention.

Claims (1)

[Claims] A communication device whose purpose is to exchange information within the device and control the operation of the device, which has means for receiving a communication signal and a transmission means for transmitting the received communication signal to another communication device. A communication device characterized in that the received communication signal can be transmitted even if the communication device is reset.