KR940008100B1 - Communication system for video information apparatus - Google Patents

Abstract

No content.

Description

Data communication method

1 is a flowchart for explaining the present invention.

2 is a diagram schematically showing its operation.

3 is a time chart for explaining the outline of the present invention.

4 is a block diagram of one embodiment of a communication system embodying the present invention.

5 is a diagram for explanation thereof.

* Explanation of symbols for main parts of the drawings

10: VTR as master device

20: Video camera as one of a plurality of slave devices

P ₁ , P ₂ : Transmission area for slave devices P ₃ , P ₄ : Transmission area for master devices

30: communication line

The present invention relates to a bidirectional data communication method between one master device and a plurality of slave devices.

In recent years, in order to enjoy the video information, for example, the production of a system including a plurality of peripheral devices such as a video camera, a television tuner unit, a timer unit, an editor, and the like, mainly on a VTR, has been conducted. In this case, the method of communication of control data such as a mode signal or various control signals becomes a problem between the VTR and each peripheral device. However, if the method of communication of this control data is unified in this system, it becomes common and generalized. It can achieve low cost.

As a method of this communication, it is conceivable to perform bidirectional communication using a VTR as a master device and a plurality of peripheral devices as slave devices. In this case there is a request to make the communication player as few as possible. This is especially true when there are a large number of slave devices.

Therefore, a method using only two of the transmission communication line and the reception communication line, or a method of performing two-way communication using only one communication line can be considered in view of the master device.

As one of the methods, the applicant has already proposed to perform bidirectional communication using only one communication line (see international application PCT / JP84 / 00425).

In other words, this method is a method in which a communication section consisting of a plurality of master device transmission areas and slave time transmission areas arranged in time division is repeated periodically, and this is a method in which only the master device manages communication time. . In this case, the transmission area for slave devices is provided by the number of slave devices.

In the case of using two transmission lines for the master device and one for the slave device, since there is only one transmission line in the slave device, the transmission from each slave device is also time-divided when performing the above periodic communication. This must be done in the transmission area that is arranged in.

However, when time-slice transmission areas are provided for all of the plurality of slave devices, the number of slave devices has a drawback in that the transmission period of each slave device becomes very long.

In addition, since there is not always a transmission request from each slave device to the master device, when a transmission area is provided to all of the plurality of slave devices as described above, a transmission area that is not used or does not need to be used is generated. Usage efficiency is bad.

In the data communication method of the present invention, a video signal having a vertical synchronization signal is processed, and in a data communication method of bidirectional communication between a master device and a slave device by connecting a master device and a slave device with a single communication line, Generating a communication start timing signal in synchronization with the period, setting a first communication section having a substantially constant phase relationship with respect to the timing signal, and transmitting the master device and the slave device through the one communication line in the first communication section. Periodically repeats communication with the network, sets an area in which the timing signal appears, detects the presence of the timing signal in the area, sets a second communication section, and responds to the detection area. The timing signal is detected within the area, and after the first communication section, the second communication section The communication is made by replacing the step is performed in the second communication period.

In addition, in the data communication method of the present invention, a video signal having a vertical synchronization signal is processed, and data is bidirectionally communicated between a master device and a plurality of slave devices by connecting a master device and each slave device with a single communication line. A communication method comprising: a first generating a communication start timing signal in synchronism with a vertical period, divided into a plurality of transmission areas set to be transmitted by the slave device, and having a substantially constant phase relationship with respect to the timing signal; Setting a communication section, periodically repeating communication between the master device and the slave device over the one communication line in the first communication section, independent of the master device, and transmitting one of the slave devices; Leave one of the set areas blank so that each slay And monitoring the state of the communication line in the device, comparing the state with the transmitted data, and ending the transmission in the area when there is a mismatch between the state of the communication line and the state of the transmitted data.

Each slave device does not specify a transmission area, but the slave device having a transmission request selects an arbitrary transmission area that is empty and transmits in that transmission area.

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

4 is an embodiment of a communication system to which the present invention is applied, and this example enables communication of serial data in two directions by one communication line. This example is an example where the master device is provided with three or more VTRs and slave devices, for example, a video camera, a TV tuner unit, an editor, and the like. In this example, only the video camera is shown.

That is, in FIG. 4, reference numeral 10 denotes a VTR, and 20 denotes a video camera.

Reference numeral 30 denotes one data communication line for transmitting control data between the VTR 10, the video camera 20, and other slave devices.

The VTR 10 is equipped with a microcomputer 110, a control unit 11 for performing communication and other control, a video circuit and mechanism deck unit 12, a function key unit 13 of the VTR, and a VTR mode display unit ( 14) and a function key unit 15 for remote control of the camera 20.

In addition, the video camera 20 is equipped with a microcomputer 210, the control unit 21 for communication and other control, the function key unit 22 of the camera, and the function key unit 23 for remote control of the VTR 10. And a display unit 24 which can be displayed in the folder, for example. In addition, motors 25F and 25Z for rotating the focus ring and zoom ring of the imaging lens, respectively, and an iris motor 25I for controlling the opening and closing of the aperture are provided in the motor drive circuits 26F and 26Z. It is connected to the control part 21 via 26I.

The function key unit 13 of the VTR 10 has function keys such as recording, playback, pause, feeding, rewinding, and stop, and when any one of these keys is operated, the microcomputer 110 of the control unit 11 is operated. Is identified and displayed on the display unit 14, and the necessary control signals are supplied to the video circuit and the mechanism deck unit 12 so that the VTR is in a mode corresponding to the operated keys.

The remote control function key section 23 of the VTR 10 on the video camera 20 also has function keys such as recording, playback, pause, feeding, rewinding, and stop. When any one of the keys is pressed, Similarly, control data is transmitted to the VTR 10 via the communication line 30 on the camera 20 side, which is input to the register of the microcomputer 110 of the control unit 11, and the contents of the data and the The mode of the VTR 10 is determined from the state of the key input of the function key unit 13 of the VTR 10, and the mode is displayed on the display unit 14, and a control signal necessary for the video circuit and the mechanism deck unit 12 is made. Is supplied to be in the state of the mode. Determining the mode of the VTR 10 from the transmission data from the camera 20 and the state of the function key 13 of the VTR 10 is for preventing misoperation, for example, a mode called feeding during camera recording. Since there is no ordinary, the feeding command is ignored at this time to continue the recording state. This is done by having the microcomputer 110 store which mode the VTR 10 should be made next for the combination of the mode of the remote control signal and the function key.

In addition, the VTR 10 conveys the signal data indicating that the mode is set to the camera 20 side, and receives it from the camera 20 side, and displays the mode of the VTR 10 on the display unit 24 in the finder. Is done.

In addition, the remote control function key unit 15 of the camera 20 of the VTR 10 has keys such as focus, iris, zoom, pan, and tilt. For example, when the zoom key is operated, zooming data is described later. Similarly, the VTR 10 is transmitted from the VTR 10 to the camera 20 through the communication line 30, and is input to the register of the microcomputer 210 of the control unit 21 of the camera 20. The zooming data is supplied to the motor drive circuit 26Z. ) Is supplied to the zoom motor 25Z to perform the zooming operation.

When the function key unit 22 is operated in the camera 20, the operation according to the key operation is performed in the camera 20 by a signal from the microcomputer 210 of the control unit 21. For example, when the zoom key is operated in the camera 20, the zooming operation is performed.

The control unit 11 of the VTR 10 and the control unit 21 of the video camera 20 are configured as follows. The control part 21 is the same structure also in another slave apparatus.

8-bit shift registers 111 and 211 are provided in the microcomputer 110 of the control unit 11 of the VTR 10 and the microcomputer 210 of the control unit 21 of the video camera 20. The shift registers 111 and 211 each have a serial input terminal SI, a serial output terminal SO, and a clock terminal CK. In addition, the shift registers 111 and 211 are configured to read and write in the state of the parallel data between the data bus of the microcomputer.

In addition, the input of serial data to the shift registers 111 and 211 and the reading of the serial data are controlled by the communication controllers 112 and 212, respectively. These communication controllers 112 and 212 control the on / off control of the input gate switches 113 and 213 and the output gate switches 114 and 214 of the shift registers 111 and 211, respectively. While generating G ₁ , G ₂ and G ₁ ′, G ₂ ′, the shift clocks CLK and CLK ′ (for one cycle, for example, 104 μsec) for the shift registers 111 and 211 are generated.

The communication controller 112 on the VTR 10 side as a master device generates a start bit in accordance with the communication start signal CS from the microcomputer 110. The communication controller 212 on the video camera 20 side of the slave device does not generate a start bit. That is, time management of communication is performed only in the VTR 10, which is a master device.

The communication controllers 112 and 212 can also be realized by a microcomputer.

115 and 215 are input transistors, 116 and 216 are output transistors, and the collectors of output transistors 116 and 216 are connected to the power supply terminals via resistors 117 and 217. At the same time, this collector is connected to the communication line 30 and the emitter is grounded. In addition, serial data from the shift registers 111 and 211 are supplied to the bases of the output transistors 116 and 216 through the output switches 114 and 214.

In addition, the communication line 30 is supplied to the bases of the input transistors 115 and 215 through the resistors 118 and 218, respectively. The emitters of the transistors 115 and 215 are grounded, and the collector is connected to the power supply terminal via resistors 119 and 219, while the collector is connected via input switches 113 and 213. The serial input terminals of the shift registers 111 and 211 are connected.

Therefore, the communication line 30 becomes the voltage of the power supply terminal (+ 5V) through the resistors 117 and 217 in the state where data is not transmitted through this, and is always in the high level + 5V state.

In the configuration as described above, the bidirectional communication between the VTR 10 as the master device and the video camera 20 as the slave device has a vertical period in synchronization with the vertical synchronization signal VD in this example as shown in FIG.

In other words, as viewed from the VTR 10 of the master device, a section consisting of four areas of the reception areas (transmission area for slave devices) P ₁ and P ₂ and the transmission areas P ₃ and P ₄ is defined as one communication section. And the rest period of a certain period is repeated in a vertical period in synchronization with the vertical synchronization signal VD. In this case, there are _two transmission areas for slave devices, P ₁ and P ₂ , which are smaller than the number of slave devices. The transmission from the slave device is performed using an empty area of the areas P ₁ and P ₂ as described later.

One bit of the start of each area P ₁ , P ₂ , P ₃ , and P ₄ becomes a start bit, but this is obtained only from the VTR 10 as a master device, and transmission and reception between the master device and the slave device are performed accordingly. That is, four start bits SB for one communication section are repeatedly generated from the communication controller 112 at regular intervals.

The transmission area and the P ₁ ~P is transmitted in each of _four serial data of 8-bit D ₀ ~D _7, thereby constituting the first word to the data D ₀ ~D ₇ of the 8 bits. In this case, since there are four communication areas in one communication section, four words of data are transmitted and received within one vertical period TF. In this way, the number of words and bits in the communication section is fixed, so that the length of the communication section is constant. Therefore, the length of the rest period is also constant.

Transmission and reception in one communication section is performed as follows. First, transmission from the master device will be described.

The communication start signal CS (FIG. 5a) is generated from the microcomputer 110 of the master device, which is supplied to the communication controller 112. This communication start signal CS is normally " 1 ", and is lowered to " 0 " when the communication start request is made. In this example, it descends four times in one vertical cycle TF. When this communication start request is made, the communication controller 112 obtains, for example, a start bit SB (Fig. 5B) which becomes a period " 1 " for a prescribed length of 104 mu sec from the time when the signal CS falls. This is supplied to the base of the output transistor 116 and supplied as a signal of "0" inverted polarity to the communication line 30 to which the collector is connected.

After the start bit SB, eight clock pulses CLK (FIG. 5C) having a clock period of 104 mu sec are obtained from the communication controller 112, which is supplied to the clock terminal of the shift register 111. FIG. In addition, the control signal G ₁ (FIG. 5 d) of the output switch 114 becomes "1" of these eight clock pulses CLK, and the output switch 114 is turned ON. In the microcomputer 110, since the transmission data DT ₁ (FIG. 5 f) is set in advance in the shift register 111, 8 bits of transmission data DT ₁ are added from the shift register 111 by the eight clock pulses CLK. It is read out and supplied to the communication line 30 through the output switch 114 and the output transistor 116. 5G is a state of a signal on this communication line 30. FIG.

When this 8-bit transmission data DT ₁ is sent out, the switch 114 is turned off, thereby raising the communication line 30 to "1". Then, this "1" period is continued for 2.5 to 5 bits. This 2.5 to 5 bit period is an end bit (see FIGS. 3 and 5 g). Normally, the end bit is about 2 bits, but in this example, all of the software is processed by the microcomputer. Therefore, the stop bit is extended above the normal flag so that the communication data is entered into or stored in another RAM of the microcomputer. I have time.

In this way, the transmission data transmitted from the master device side in this transmission area is supplied to the base of the input transistor 215 on the video camera 20 side of the slave device, for example. Then, at the start bit SB, the input transistor 215 is turned off, and its collector output rises to " 1 ". Then, this is detected by the communication controller 212 so that the control signal G ₁ ′ (FIG. I) of the input switch 213 becomes “1” and at the same time, clock pulse CLK 'with eight cycles of 104 μsec (FIG. 5 k). ) Is obtained, and the switch 213 is turned on and the clock pulse CLK 'is supplied to the clock terminal of the shift register 211. Therefore, the transmission data DT ₁ from the VTR 10 is input to this shift register 211. Then, the input data is transferred to the RAM of the microcomputer 210 in the stop bit period and stored therein, and data DT ₂ sent from the video camera 20 to the VTR 10 is transferred to this shift register 211. Is set.

At this time, the data DT ₁ is also input to other slave devices at the same time, but whether the data DT ₁ is used in the slave device is determined by reading the contents with each microcomputer.

Next, the reception area as viewed from the master device side, that is, transmission of the slave device will be described.

Now, if there is a transmission request from the video camera 20, and the transmission request signal DM is supplied to the communication controller 212, the video camera 20 is in a transmission standby state, and the shift register 211 is provided with transmission data DT ₂ ( Right side of FIG. 5 h is stored.

In this state, a start bit SB is generated in the communication controller 112 of the VTR 10 at the start of the area P ₁ , which is loaded on the communication line 30 via the transistor 116 and transmitted to the video camera 20. . Then, as shown in the right side of FIG. 5G, the data on the communication line 30 is in the state of 1 bit period "0". Therefore, the input transistor 215 of the video camera 20 is turned off, and its collector output becomes "1". The communication controller 212 detects this and the control signal G ₂ ′ (FIG. 5 j) of the output switch 214 becomes “1”, so that this output switch 214 is turned on and eight clock pulses. CLK generated in the "1" period of a 'is the signal G ₂ ", and this is supplied to the clock terminal of the shift register 211. Therefore, the data DT ₂ is read out from this shift register 211 (see FIG. 5 h), and is supplied to the communication line 30 via the output transistor 216.

On the other hand, after the start bit SB is output from the communication controller 112 on the VTR 10 side, the control signal G ₂ (FIG. 5) of the input switch 113 becomes "1", and this input switch ( 113) is at the same time, the signal G ₂ is turned on, the eight clock pulse CLK (FIG. 5 C) is obtained in the period in which "1".

Therefore, the data DT ₂ transmitted from the video camera 20 is supplied to the shift register 111 through the input transistor 115 and the switch 113, and is input to the shift register 111 by the clock pulse CLK.

Then, it is transferred to and stored in the RAM of the microcomputer 110 in the end bit period of the transmission area P ₁ .

The above is a case where the first area P ₁ of the communication section is not used as a transmission area of another slave device, but when this area P ₁ is also used as a transmission area of another slave device, the collision of areas is avoided as follows. Therefore, the transmission area of one slave device is switched to the next area P ₂ .

1 is a flowchart for it, and the program according to this flowchart is executed by the microcomputer of the control unit of each slave device.

That is, when the start bit is transmitted to each slave device at the head of the area P ₁ from the master device, the transmission data is sent to the communication line 30 as described above in the slave device having a transmission request (step 101). At this time, the data sent to the communication line 30 and the state of the communication line 30 are checked for each bit (step 102). That is, if the communication line 30 is sent out data, the output transistor 216 is turned off. Therefore, the state becomes 5V, and if the data is "1", the output transistor 216 is turned on, so that it becomes 0V.

By the way, when the transmission data is transmitted from a plurality of slave devices, when the data bit from any one of the slave devices becomes "1", the output transistor 216 is turned on, so that any data of another slave device Though, it goes down to 0V. Therefore, by detecting that the communication line 30 is 0V even though the bit of the transmitted data is "0", the difference between the transmitted data and the data transmitted to the communication line 30 is detected (step 103). At the same time, it is detected that another slave device is being transmitted in this area P ₁ . As can be seen from the above, when a collision occurs such that two or more slave devices transmit in the same transmission area, the slave device in which the transmission data bits D _{0 to} D ₇ send "1" as soon as possible. Is given priority, and the area becomes the transmission area of the slave device. Then, in the slave device where it is detected that the transmission data and the data communicated on the communication line 30 are different for each bit, all subsequent bits become "0", and the transmission data of the slave device whose area P ₁ is determined as the transmission area. The occurrence of communication error is prevented.

In this way, in the slave device that could not transmit in the area P ₁ , the transmission data is again sent out by the start bit SB arriving at the beginning of the area P ₂ (step 104). As described above, whether or not the area P ₂ is empty is performed by checking for each bit in steps 105 and 106, and is empty, and this area P ₂ is selected as the transmission area of the slave device. If not empty, it is again determined whether or not the area P ₁ is empty in the next cycle, and the above operation is repeated until the next empty area is detected.

2 schematically shows the above operation. In this example, the transmission request collides with the slave device I (e.g. tuner) and slave device II (e.g. editor) in area P ₁ , and the editor of slave device II is shown. in the area P ₂ indicates that switching the transmission area.

The bit-by-bit check can be facilitated by setting the number of stages of the shift register 211 to nine stages. In practice, the current shift register with built-in 4-bit microcomputer has 9 stages, so it can be used as it is.

If more than the idle period in the area P ₁ ~P ₄ made after communication section, such as, VTR (10) and according to the video camera 20, or other slave devices, is a process in accordance with the received data content carried out at the same time the The operation is also made by time division processing.

Next, similarly, the communication section in which transmission from the VTR 10 and transmission from a slave device such as the camera 20 is made into one block is periodically repeated with the rest period in between. In this example, since the start bit is generated only in the master device, and the master device side manages time, the areas P _{1 to} P ₄ can be reliably distinguished, and the communication and idle sections are clearly distinguished. do.

As described above, since the communication is performed periodically, even if there is a loss of communication or a communication miss can be returned to the correct contents immediately.

In addition, in the above example, since communication and other operations can be performed by a single chip microcomputer without using an expensive interface, bidirectional digital data communication is generally performed by a low-cost consumer LSI and one communication line. It can be realized.

Since the communication period is taken from the master device side, even when a plurality of operations other than the communication must be processed by time division, one operation is not stopped midway.

The start bit SB in the communication controller 112, the generation of the clock pulse, the start bit detection in the communication controller 212 and the generation of the clock pulse may be performed by microcomputer control, respectively. As in the example of the figure, hardware other than the microcomputer may be installed.

In addition, the above example is a special example in which one communication line can be used. However, the present invention can also be applied to the case where two transmission lines and a receiving line are disposed in the master device and a plurality of slave periods, respectively. to be.

The check of whether or not the transmission area is empty may be performed for each word (8 bits).

As described above, in the present invention, since the transmission from the slave device is performed by using an arbitrary empty area among the plurality of time division areas, the number of time division areas is at least smaller than the number of slave devices, and the number of unused areas decreases, resulting in the use efficiency. Also good. In addition, when performing communication at a constant period, for example, a vertical period, the length of the communication section does not need to be unnecessarily long, and therefore, it is possible to take sufficient time for operations other than communication performed in the idle section.

Claims (2)

In a data communication method in which a video signal having a vertical synchronization signal is processed, and a master device and a slave device are connected by a single communication line, and bidirectionally communicates between the master device and the slave device, the communication start timing is synchronized in synchronism with the vertical period. Generates a signal, sets a first communication section having a substantially constant phase relationship with respect to the timing signal, and periodically communicates between the master device and the slave device through the one communication line in the first communication section. Is repeated, the area in which the timing signal appears is set, the presence of the timing signal is detected in the area, the second communication section is set, and the time difference signal is detected in the area in response to the detection area. Detects and replaces the communication with the second communication section after the first communication section. A data communication method comprising steps performed in a second communication section. In a data communication method in which a video signal having a vertical synchronization signal is processed, and a master communication device and each slave device are connected by a single communication line, and the two-way communication is performed between the master device and the plurality of slave devices. Generate a communication start timing signal, and are divided into a plurality of transmission areas set to be transmitted by the slave device, and set a first communication section having a substantially constant phase relationship with respect to the timing signal; In the communication section, communication between the master device and the slave device is periodically repeated through the one communication line, and one of the set areas is independent of the master device and is transmitted so that one of the slave devices can transmit. Leave blank and state of communication line in each slave device Monitoring, and data communication method which comprises the step of end of transmission in the area compare the state with the transmission data and, if there is a mismatch between the data transmitted and the state of said communication line state.

Images