JPH02201518A - Control system for video device - Google Patents

Abstract

PURPOSE:To visually reduce the noise appearing on a reproduced picture by transmitting data among plural computer devices in the vertical blanking period of a video signal synchronously with the vertical synchronizing signal of the video signal. CONSTITUTION:This control system consists of a video system 1, a bus line 2, MPUs 3a to 3c, and a transmission control part 4 provided with an edge extracting circuit 5 and an one-shot circuit 6. At the time of data transmission among MPUs 3a to 3c, a communication enable signal EN having a prescribed pulse width is generated based on a signal synchronized with the vertical synchronizing signal of the video signal, for example, a magnetic head switching signal SW of a VTR and data is transmitted in the effective period of this signal EN. In this case, the effective period of the signal EN is set within the vertical blanking period of the video signal. Thus, noise does not appear on the reproduced picture though the video signal is affected by data transmission.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control method for video equipment, such as a video tape recorder, that processes video signals, by using a plurality of computer devices, and particularly relates to a method for controlling video equipment that processes video signals, such as a video tape recorder. This reduces the influence of data transmission between devices on video signals.

[Conventional technology]

Devices that process video signals, such as video tape recorders and video disc playback devices, have many functions, and in order to realize these functions, control by a microcomputer unit (hereinafter referred to as MPU) is essential. It has become. In particular, recently, due to the variety of monkey functions and the complexity of control, multiple MPUs are operated in parallel as shown in Figure 4. The part that performs recording or playback; in the case of a VTR, there is a recording system that records video and audio signals from the tuner circuit or line input circuit onto magnetic tape, and a recording system that reads the video and audio signals recorded on the magnetic tape and outputs them externally. It consists of a playback system that outputs.

The video system l connects a plurality of MPs via a path line 2.
It is connected to U 3 a + 3 b t 3 c and controlled by these MPUs 3 a to 3 C? It will be ffff. These MPUs 3a to 3c mutually transmit and receive data via the path line 2 and operate in synchronization with each other.

By the way, data transmission methods for transmitting digital signals include parallel transmission methods, which use transmission lines for the number of bits to send one code at a time, and serial transmission methods, which use only one transmission line and send bits in temporally divided manner. There is a transmission method. VTR
In general, the serial transmission method is adopted because the number of transmission lines is small and the input/output ports of the MPU can be used effectively. Recently, MPUs for signal processing or control have also been provided with built-in interfaces for serial transmission, and VTRs and the like have adopted a clock synchronous serial transmission method.

Figure 5 is a time chart for explaining the clock synchronous serial transmission method, where the transmitting side sets serial data DT at the falling edge of the clock signal CK, and the receiving side recognizes the serial data DT at the rising edge of the clock signal CK. do. The frequency of the clock signal CK is 100K IIz
= I M I (about z.

When the transmitting side generates data to be transmitted, it issues a transmission request to the receiving side, and if the receiving side is in a receivable state, it outputs a transmission permission to the transmitting side. Upon receiving transmission permission, the transmitting side sends out the clock signal CK and serial data DT in units of bytes, and when the predetermined number of bytes or the required number of bytes has been transferred, it clears the transmission request, and receives it. The side also clears the transmission permission and completes one transmission.

[Problem to be solved by the invention]

A large amount of data signals and clock signals are outputted onto the lot line 2 that connects the plurality of MPUs 3a to 3c, and each MPU 3a to 3c is arranged on a separate printed circuit board due to the system configuration. For this reason, the pass lines 2 are arranged around the board, and the patterns are arranged close to each other, especially in the case of a board mounted with high density such as a VTR. As a result, the cycle of the clock signal and its harmonic components may become noise that affects nearby patterns, noise may enter the video head or amplifier, and the power supply voltage may be lower than that of the clock signal due to the influence of the clock signal. Sometimes it is shaken by the cycle.

The video head reproduction output of a VTR is minute, on the order of several microvolts, and requires considerable amplification to reach the level required for signal processing. For this reason, slight fluctuations in the power supply voltage or incoming noise will adversely affect the video signal. In particular, in a system in which multiple MPUs 3a to 3C are connected via path line 2, such as in conventional video equipment, each MPU
PU3a to 3c operate independently, and the MP
Data transmission between U is not synchronized with the video signal, and
Since this is performed depending on the internal processing cycle of the PU, there is a problem that dot-like noise appears on the playback screen.

An object of the present invention is to visually reduce noise that appears on a playback screen as a result of the influence of data transmission between a plurality of MPUs on a video signal.

[Means to solve the problem]

In a control method for video equipment in which video equipment that processes video signals is controlled by a plurality of computer devices, data transmission between the plurality of computer devices is synchronized with a vertical synchronization signal of the video signal, and This should be done within the blanking period.

[Function] When transmitting data between multiple computer devices, a communication enable signal having a predetermined pulse width is generated based on a signal synchronized with a vertical synchronization signal of a video signal, for example, a magnetic head switching signal of a VTR. This should be done during the valid period of the communication enable signal.

In this case, by setting the effective period of the communicable signal within the vertical blanking period of the video signal, noise does not appear on the playback screen even if the video signal is affected by data transmission.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of a control system for video equipment according to the present invention, and the same parts as in FIG. 4 are given the same reference numerals and will be described.

In this embodiment, in the case of a VTR, the video system 1 is a part that records and reproduces video signals.
Controlled by 3c.

A plurality of MPs (J3a to 3c) mutually transmit and receive data via the path line 2 and operate in synchronization with each other.

The transmission control unit 4 controls data transmission between the MPUs 3a to 3C via the path line 2, and extracts the falling and rising edges of the switching signal SW supplied from the video system 1 using the edge extraction circuit 5. Using this extracted edge as a starting point, the one-shot circuit 6 outputs a signal having a predetermined pulse width as a communication enable signal EN.

The MPUs 33 to 3c receive this signal EN and send and receive data.

The switching signal SW is a switching signal for alternately switching two video heads mounted symmetrically at 180 degrees on a rotating drum for winding a magnetic tape to be loaded into the video system 1. 2 of vertical synchronization signal
This is a signal with a frequency of 30 Hz and a period twice that of the previous one.

The relationship between the video signal and the switching signal SW is as shown in the waveform diagram in Figure 2, where the switching signal SW is a few H (H:
horizontal synchronization interval), for example, about 6 H before.

In the transmission control section 4, an edge extraction circuit 5 extracts the edge of the switching signal SW, and a one-shot circuit 6 generates a pulse signal having a predetermined width starting from the edge as a communication enable signal EN. The pulse width of this pulse signal is set to about 24 H, for example. The reason why it is set to 24H is that the effective line of the video signal starts from the 18th line counting from the leading edge of the vertical synchronizing signal, so it becomes about 24 (=6+18) lines counting from the leading edge of the switching signal SWO. Therefore, this pulse signal is included in the vertical blanking period.

The communication enable signal EN obtained in this way is used by MPU3a to 3C.
and the MPUs 3a to 3C receive this communication enable signal EN.
Data transmission is performed within the validity period of .

Next, the internal processing method of the transmitting MPU will be explained with reference to the flowchart shown in FIG.

First, the transmitting MPU waits until the communication enable signal EN becomes valid (step 31). If the communication enable signal EN is enabled and there is data to be sent to the transmitting MPU (step S2), the enable state of the communication enable signal EN is monitored (step S3): If it is valid, 1-byte serial transmission is performed. (Step S4). After the transmission is completed, the process returns to checking the presence or absence of transmission data (step S2) and repeats the above-described processing until there is no more data to be transmitted (step 32) or the communication enable signal EN becomes invalid.

Even if the communication enable signal EN becomes valid (step SL), if there is no data to be transmitted (step S2), the process immediately ends.

As shown in 2, before executing 1-byte serial transmission, it is determined whether the communication enable signal EN is valid or not, and if it is not valid, serial transmission is not executed, so serial transmission is always performed only within a predetermined period. It turns out. Communication enable signal EN
Since the effective period of the video signal is set approximately equal to the vertical blanking period of the video signal, even if the video signal is affected by the clock signal CK due to data transmission, no noise will appear on the playback screen and the visual The above noise can be significantly reduced.

In the above-described embodiment, the communication enable signal EN is generated based on the edge of the switching signal SW, but the present invention is not limited to this, and the vertical synchronization signal of the video signal may be used as the reference. Also, instead of the one-shot circuit for setting the valid period of the communication enable signal EN, an MP activated by the switching signal SW is used.
A timer inside U may also be used.

It goes without saying that the present invention is not limited to VTRs and may be applied to devices that handle video signals, such as video disk playback devices.

〔Effect of the invention〕

According to the present invention, a video signal is affected due to data transmission between multiple computer devices in video equipment,
As a result, the noise generated on the playback screen can be visually significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the control system for video equipment according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, and FIG. 3 is a diagram for explaining the operation of FIG. 1. FIG. 4 is a block diagram for explaining the conventional control method for video equipment, and FIG. 5 is a waveform diagram for explaining the operation of the serial transmission method. 1...[1G image system, 2...pass line, 3
a~3C...MPU, 4...Transmission control unit, 5...
Edge extraction circuit, 6... one-shot circuit. Waveform diagram Fig. 2

Claims (1)

[Claims] A control method for video equipment in which video equipment that processes video signals is controlled by a plurality of computer devices, comprising: synchronizing data transmission between the plurality of computer devices with a vertical synchronization signal of the video signal; A control method for video equipment, characterized in that the control method is performed within a vertical blanking period of the video signal.