JPS6141346Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a key input circuit using a microcomputer in a magnetic recording/reproducing device (hereinafter referred to as "VTR"). β) mode, the present invention relates to a key input circuit that can prohibit predetermined key operations of a VTR in a predetermined mode.

FIG. 1 is an illustrative diagram showing an example of a key input matrix circuit using a conventional microcomputer, which is the background of this invention. The microcomputer 1 has output terminals 01, 02, 03 for deriving scan signals (for example digit timing signals) and input terminals 11, 1 for key input signals.
Including 2,13. It goes without saying that the microcomputer 1 includes an arithmetic operation logic unit, RAM, ROM, etc., although not shown. The output terminals 01, 02 and 03 are connected to column lines C1, C2 and C3 forming the key matrix 2. Further, key input terminals 11, 12 and 13 are connected to row lines R1, R2 and R3 of matrix circuit 2. Key switches K1, K2, . . . , K9 are provided at the intersections of each column line and row line. For example, when the key switch K1 of the key input matrix circuit 2 is turned on, the scan signal 01 from the microcomputer 1 is input to the key input terminal 11 via the column line C1, this key switch K1, and the row line R1. Therefore, at this timing, the other input terminals 12 and 13 are at low level (hereinafter simply "L"). , input terminals 11, 12
Based on the signals inputted to and 13, which key switch is turned on is detected. The microcomputer 1 then performs calculations and the like in response to the key switch being turned on. Such a key input matrix circuit is characterized in that key input signals from a large number of key switches can be inputted with a relatively simple configuration.

On the other hand, recently, microcomputers have been used for various purposes, for example, as control circuits for VTRs. For example, the VTR operation keys include "play", "fast forward", "rewind", "dubbing", "record", "lock", and "stop".
,
For example, 11 keys are provided, such as "pause", "still image", "picture search forward", and "picture search backward". And these
The 11 keys are composed of a key input matrix circuit as shown in FIG. In "picture search forward forward" or "picture search reverse forward", the tape is run rapidly in the forward or reverse direction to display the reproduced image, thereby making it possible to quickly find (search) a desired image. Such a picture search has a problem in that noise increases due to shifts in horizontal synchronization signals due to playback in a direction across the video track. As shown in Figure 3, for example, in a 3-hour recording (β), there is little noise because the horizontal synchronization signal deviation of adjacent video tracks is small, but in the case of a 2-hour recording (β), the noise is small in the case of a 2-hour recording (β). There is a lot of noise because the horizontal synchronization signal between tracks has a large deviation. For this reason, for example, in the case of two-hour recording (β), it is desirable to prohibit the key inputs of "picture search forward" and "picture search backward".

Also, generally speaking, if a VTR with multiple recording and playback modes could automatically prohibit predetermined key operations in a certain mode, it would be possible to prevent the appearance of the noisy playback screen as described above, and to It could also be used to protect the magnetic head.

FIG. 4 is a circuit diagram showing an example of a conventional key input circuit capable of inhibiting key input, which is the background of this invention. In the conventional device shown in FIG.
2 etc. is prohibited from being input. That is, input signals from key switches K1 and K2, for example, are applied to one input of each of NAND gates 31 and 32. Further, a key input prohibition signal (KS signal) is connected to the other input of each of these NAND gates 31 and 32. The outputs of the NAND gates 31 and 32 are applied to the bases of transistors 41 and 42 inserted in the scan signal path, respectively.
The transistors 41 and 42 are operated in a switching manner. For example, the key input prohibition signal (KS
signal) is given, the key switch K1
In this case, both inputs of the NAND gate 31 become L, and its output becomes a high level (hereinafter simply referred to as "H"). Therefore, the transistor 41 is turned off, and input of the scan signal (SC signal) to the input terminal 11 is prohibited or cut off. Then, when there is no key input prohibition signal (KS signal), NAND
When the corresponding key switches K1 and K2 are turned on, the outputs of the gates 31 and 32 become L, making the corresponding transistors 41 and 42 conductive, and allowing input of scan signals (SC signals) to the input terminals 11 and 12. do. In this way,
A key input prohibition signal is used to prohibit the corresponding key input, but in the conventional system shown in FIG. There was a problem that the number of parts such as transistors and accompanying transistors increased.

Therefore, the main purpose of this invention is to create a VTR that can prohibit predetermined key operations in a predetermined mode in a VTR that has multiple recording and playback modes, and that can achieve this with a simple configuration.
The purpose of the present invention is to provide a key input circuit for.

The above objects and other objects and features of the present invention will become clearer from the following detailed description with reference to the drawings.

FIG. 5 is an illustrative view of the main parts showing an embodiment of this invention. Although this embodiment shows only one column line and one row line, those skilled in the art will easily configure it as a matrix circuit including a plurality of column lines and row lines, as shown in FIG. .

In the embodiment shown in FIG. 5, a resistor 41 constituting the scan signal control circuit 4 is inserted between the key switches K1 and K4 of the column line 1. Here, switch K1 is, for example, a "playback" switch, and switches K4 and K7 are, for example, a "picture search forward" switch and a "picture search backward" switch that are to be disabled in the 2-hour recording (β) mode. be. resistance 41
One end of a resistor 42 is connected to the connection point between the key switch K4 and the contact point of the key switch K4, and the other end of the resistor 42 is connected to the collector of a transistor 44 via a diode 43. A two-hour recording (β) mode selection signal (KS signal) is applied to the base input of this transistor 44, and its emitter is grounded. The cathode of the diode 43 and the collector of the transistor 44 are both connected to the positive power supply +B via a resistor.

In operation, consider the case where the 2-hour recording (β) mode selection signal (KS signal) is input at H level. In this case, the transistor 44 constituting the scan signal control circuit 4 becomes conductive, and the diode 4
3 also becomes conductive. Therefore, the scan signal applied from the output terminal 01 of the microcomputer 1 to the column line C1 passes through the resistor 41, and then is shunted or bypassed to a path of the resistor 42, the diode 43, and the transistor 44. Therefore, even if the key switch K4 is turned on at this time, by appropriately selecting the resistance value R1 of the resistor 41 and the resistance value R2 of the resistor 42, the voltage at the input terminal 12 is lower than the threshold voltage of the microcomputer 1. This means that only the following signals can be given. Therefore, the microcomputer 1 cannot detect the key input signal at that time, and key input is essentially prohibited.
The same applies to the operation of key switch K7. However, for key switch K1, 2
It can be input at any time regardless of whether the time recording (β) mode selection signal (KS signal) is H or L.
Furthermore, when the key input signal is L, the transistor 44 is non-conducting, so if the key switch K4 or K7 is turned on, the key input signal higher than the threshold voltage of the microcomputer 1 is applied to the input terminal 12 or 13 at that timing. A signal may be provided and a normal keystroke operation may occur.

FIG. 6 is a circuit diagram showing the main parts of another embodiment of this invention. In this embodiment, a pnp transistor 4 is connected between key switches K1 and K4 of column line C1.
Insert 5. The base of this transistor 45 receives a key input inhibit signal via a resistor. At the same time, the base of this transistor 45 is further connected to the positive power supply +B via a resistor. In addition, also in the embodiment shown in FIG. 6,
Although only one column line is shown, the first
It will be easily understood that the circuit can be configured into a matrix circuit as shown in the figure.

In operation, when the 2-hour recording (β) mode selection signal (KS signal) is H, the transistor 45
is cut off, and the scan signal applied to column line C1 is not applied to key switches K4 and K7. Therefore, even if the key switch K4 or K7 is turned on at this time, no signal is given to the corresponding input terminal 12 or 13, and in the microcomputer 1, the key switch K is turned on.
4 or K7 key input cannot be detected. At this time, key switch K1 is set to record for 2 hours (β).
Key input is always possible regardless of the mode selection signal (KS signal). Then, 2 hours of recording (β
) When the mode selection signal (KS signal) becomes L, this transistor 45 becomes conductive, and a scan signal can also be applied to key switches K4 and K7, so that a normal key input operation is performed.

As described above, according to this invention, predetermined key operations can be prohibited during a predetermined recording/playback mode (for example, the 2-hour recording (β) mode, which is a relatively short-time recording/playback mode). It is possible to prohibit the appearance of a desired noisy playback screen.

[Brief explanation of the drawing]

FIG. 1 is an illustrative diagram showing an example of a key input matrix circuit using a microcomputer, which is the background of this invention. FIG. 2 is a timing diagram when the key switch K1 in FIG. 1 is turned on. FIG. 3 is an illustrative diagram showing an example of a β method and a β method video track. FIG. 4 is a circuit diagram showing an example of a key input circuit having a conventional key input prohibition circuit, which is the background of this invention. FIGS. 5 and 6 are circuit diagrams showing essential parts of an embodiment of this invention, respectively. In the figure, 1 is a microcomputer, 2 is a key input matrix circuit, and 4 is a scan signal control circuit.

Claims (1)

[Claims for Utility Model Registration] (1) A magnetic recording and reproducing device having at least two modes: a predetermined relatively long-time recording and reproducing mode and a relatively short-time recording and reproducing mode. A key input circuit, wherein the magnetic recording and reproducing device includes, as an operation key,
a microcomputer that includes at least a special playback command key in addition to a normal playback command key, and has an input terminal for the special playback command key; a scan signal for key input is derived from the microcomputer to the special playback command key; a scan signal path; inserted into the scan signal path to prohibit the scan signal from being applied to the special play command key when the mode of the magnetic recording/reproducing device is a predetermined mode of the at least two modes; A key input circuit for a magnetic recording/reproducing device, comprising a scan signal control circuit for controlling the scan signal. (2) The scan signal control circuit is configured as a bypass means, and the bypass means is activated when the key input prohibition signal is applied to bypass the scan signal in the scan signal path. A key input circuit for a magnetic recording/reproducing device according to claim 1. (3) The scan signal control circuit is configured as a cut-off means, and the cut-off means cuts off transmission of the scan signal after the key input prohibition signal is given. A key input circuit for the magnetic recording/reproducing device described in 1.