KR920004217B1 - 4 head switching control head and method thereof - Google Patents

Abstract

The circuit includes a microprocessor (10) for controlling a timer and the whole system. A first switching means performs rotary switching under the control of the microprocessor (10) to decide which of four heads is to be selected so as to carry out a reading function. A second switching means performs head amplification switching under the control of the microprocessor (10) to decide which of four heads is to be selected to carry out a reading function. The first and second switching means are controlled by the combination of envelope signals and head switching signals. The circuit improves the picture quality and saves the manufacturing cost.

Description

4-head change over control circuit and method

1 is a circuit diagram according to the present invention.

2 is a flow diagram of a head switch pulse interrupt in the present invention.

3 is a flow chart for controlling envelope terminals in the present invention.

* Explanation of symbols for main parts of the drawings

10: microcomputer Q1-Q6: 1-6 transistor

D1-D4: Diode R1-R5: Resistance

The present invention relates to a head switching control circuit and a method of a video cassette recorder (hereinafter referred to as a VCR), in particular a double azimuth (hereinafter referred to as DA) a four-head model It relates to a head switching control circuit and a method). Conventional DA 4-head VCRs use a two-chip Micom to reproduce good image quality in multi-function, that is, still and slow search modes. Since the system consists of two microcomputers, the system control part, which should be controlled by accurate timing, is not affected by the data processing part. However, since two microcomputers are required, there was a problem that the risk of cost increase and development.

Accordingly, an object of the present invention is a four-head switch control circuit and a method for controlling head switching without a time delay by controlling a scissor and a timer with one chip microcomputer in a DA four-head VCR.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a circuit diagram according to the present invention, in which a microcomputer 10 for controlling a ciscon and a timer, and which head of four heads is read by the microcomputer 10, is selected by the control of the transistor for switching the switching. The first switching switching means consisting of (Q4-Q6) and diodes D3 and D4 and resistors R4 and R5, and which head of the four heads is read by the microcomputer 10 control to select a head amplifier. Second switching means consisting of transistors Q1-Q3, diodes D1-D2, and resistors R2, R3 for switching switching, an envelope signal and a head switching signal indicative of which channel is being scratched. And control means for controlling the first and second switching switching means.

2 is a flowchart of a head switch pulse interrupt in accordance with the present invention.

3 is a flowchart for controlling an envelope terminal according to the present invention.

Based on the above-described configuration, the present invention will be described in detail with reference to FIGS. 1-3. First, as shown, the envelope terminal ENV of the microcomputer 10 is supplied to the bases of the transistors Q2, Q3, Q5, and Q6 through the resistors R8, R10, R14, and R16, respectively. The control signal 1 can be selected. Resistors R9, R11, R15, and R17 are connected between the base terminal and the emitter terminal of each of the transistors Q2, Q3, Q5, and Q6.

The head amp switch signal HAS and the rotary switch signal RS send the outputs of the head amp terminal HD AMP and the rotary terminal ROTARY of the microcomputer 10 as they are. In synchronism with the envelope detection signal ENV DET, it is selected whether to output in-phase or inverse phase. When the high signal is output to the envelope terminal ENV of the microcomputer 10, the control signal 1 becomes high regardless of the envelope detection signal ENV DET, thereby turning on the transistors Q3 and Q6 and turning the transistors on. Turn off (Q2, Q5).

Therefore, the output signal of the head amplifier terminal HD AMP and the output signal of the rotary terminal ROTARY are output as the head amplifier switch signal HAS and the rotary switch signal RS through the diodes D1 and D3, respectively.

When the envelope terminal ENV is input and becomes high impedance, the control signal 1 becomes the envelope detection signal ENV DET itself through the resistor R1. At this time, the signal applied to the diodes D1 and D3 is in phase with the envelope detection signal ENV DET and the signal applied to the diodes D2 and D4 is reversed with the envelope detection signal ENV DET.

The resistors R3 are connected to ground through the cathode terminals of the diodes D1 and D2, and the resistors R5 are connected to ground through the cathode terminals of the diodes D3 and D4. Therefore, when the output of the head amplifier terminal (HD AMP) and the rotary terminal (ROTARY) is high, this high signal is inputted through the resistors R6 and R12 to the base terminals of the transistors Q1 and Q4 so that the transistors Q1 and Q4 Since each is turned on, power supply 5V is grounded through each of resistors R2 and R4. The resistors R7 and R13 are connected between the base terminal and the emitter terminal of each of the transistors Q1 and Q4. As a result, power is not supplied to the transistors Q3 and Q6 and is supplied only to the transistors Q2 and Q5 so that the in phase is output to the head amplifier switch signal HAS and the rotary switch signal RS.

On the contrary, when the output of the head amplifier terminal HD AMP and the rotary terminal ROT is low, the reverse phase is output to the head amplifier switch signal HAS and the rotary switch signal RS. The flowchart illustrating a process of controlling signals of the envelope terminal ENV, the head amplifier terminal HD AMP, and the rotary terminal ROTARY in the microcomputer 10 will be described.

First of all, the head amp terminal (HD AMP) and the rotary terminal (ROTARY) are controlled. This routine is a part of the routine that is synchronized with the edge of the headswitch pulse. Check the authorization in the microcomputer 10 and performs step (2A) in the play mode. In the step (2A), it is determined whether the SP (Standard play) mode is performed in step (3A) if the SP mode, and (5A) if not in the SP mode. In step (3A), the low signal is output to the head amp terminal (HD AMP), and in step (4A), the signal output to the rotary terminal (ROTARY) is in phase with the head switch and then returns. In step (5A), the high signal is output to the head amplifier terminal (HD AMP), and in step (6A), the signal output to the rotary terminal (ROTARY) is reversed with the head switch and returned.

If it is not the play mode in the step (1A), check whether the current mode is still (Still) mode in step (7A), and if it is not the still mode (8A), and if it is still mode (11A).

In step (8A), it is checked whether the current mode is the double speed mode, and if it is not the double speed mode, step (9A) is performed. If the mode is double speed mode, step (11A) is performed. In the step (9A), it is checked whether the current slow mode (Slow) mode (16A) is performed if the slow mode is not, and if the slow mode (10A). In step (10A), if the moving period is checked by checking whether the tape movement period is performed, perform step (19A), and if not, perform step (11A) and check whether the SP mode is again, and then, in step SP (12A) If no, the SP mode is performed (14A). In step 12A, the signal output to the head amplifier terminal HD AMP is reversed to the head switch. In step 13A, the high signal is output to the rotary terminal ROTARY and returned. In step 14A, the signal output to the head amplifier terminal HD AMP is in phase with the head switch. In step 15A, the low signal is output to the rotary terminal ROTARY and returned. In step (16A), it is checked whether the present mode is F. ADV (Frame Advance) mode, and if it is this mode, step (10A) is performed. If this mode is, step (17A) is performed. In step (17A), it is checked if the current mode is search (Search) or returns, and if it is search mode, step (18A) is performed.

In step (18A), it is checked whether the SP mode is present, and if it is not the SP mode, step (5A) is performed.

In step 19A, a high signal is output to the head amp terminal HD AMP and step 20A is performed. In step (20A), it is checked whether the head switch is high, and if it is high, step (21A) is performed; otherwise, step (22A) is performed. In step 21A, the low signal is output to the rotary terminal ROTARY and then returned. In step 22A, the signal is returned after the high signal is output to the rotary terminal ROTARY.

In addition, a flow diagram illustrating a process of making the envelope terminal ENV as an input by determining a portion that needs to be synchronized with the envelope detection signal ENV DET as a portion for controlling the envelope terminal ENV will be described. In step (1B), check whether the tape speed is SP. If the SP is SP, perform step (2B). If not, perform step (7B).

In step (2B), it is checked whether the current search mode is performed, and if it is a search mode, step (6B) is performed. If it is not a search mode, step (3B) is performed.

In step (3B), it is checked whether the current mode is F. ADV mode, and if step F.ADV mode is not performed, step (4B) is performed. If step F.ADV mode is performed, step (5B) is performed. If it is a slow mode and checks whether it is a mode, the step (5B) is performed. If it is not the slow mode, step (7B) is performed, and in step (5B), it is checked whether the tape movement period is performed, and if step (7B) is not the movement period, step (6B) is performed. In step (6B), the envelope terminal (ENV) is designated as an input port and returned. In step (7B), the high signal is output from the envelope terminal (ENV). When the envelope terminal ENV is outputting a high signal, the signals of the head amplifier terminal HD AMP and the rotary terminal ROTARY are directly output as the head amplifier switch signal HAS and the rotary switch signal RS. It's a process that keeps you motivated.

On the other hand, if the envelope terminal (ENV) is high impedance, that is, designated as an input port, the rotary switch signal (RS) and the head amplifier switch signal (HAS) must be synchronized with the envelope detection signal (ENV DET). The HD AMP and the rotary terminal ROTARY determine whether to output the in-phase signal of the envelope detection signal ENV DET or the reverse phase signal.

As described above, the image quality can be prevented from being degraded by the time delay generated when controlling the scones and timers with a single microcomputer in the DA 4-head VCR. There is an advantage.

Claims (2)

In the four-head switching circuit of a video cassette recorder, a microcom 10 for controlling a system and a timer and a head of the four heads are selected by the microcomputer 10 to control rotary switching. A state in which the first switching switching means for switching the head and the second switching switching means for switching the head amp switching are selected by the microcomputer 10 control of which of the four heads is read. And a control means for controlling the first and second switching switching means by a combination of an envelope signal and a head switching signal. In the four-head switching method of the video cassette recorder, if the current mode is the play mode and the SP mode, the output signal is low to the head amplifier terminal, and the signal of the rotary terminal is in phase with the head switch. A second step of checking whether the tape movement period is present if the current is not the play mode, the still mode and the double speed mode, and the current mode is the slow mode or the F. ADV mode, and in the second process In the SP mode instead of the tape movement period, the third step of performing the opposite operation to that of the SP mode when the head amplifier terminal signal is reversed and the high signal is output to the rotary terminal. If the current mode is not F.ADV mode, it is search mode and it is SP mode, high signal is outputted to head amplifier terminal. If the head switch is not high while outputting low low, the fourth step of outputting high to the rotary terminal, and if the tape spread is in SP mode, the current is not in search mode, and the current is in F.ADV mode or slow mode, the envelope is enveloped. And a fifth process of outputting high from the envelope terminal when the terminal is designated as an input port and the tape spread is not in the SP mode, the slow mode, or the tape movement period.

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