DATA TRANSMISSION SYSTEM

Abstract: A data transmission system for transmitting between a main apparatus such as a portable video tape recorder and exterior additional sub-apparatus such as a video camera, tuner, etc. a remote control signal and a data signal which define the operating mode of the aforesaid apparatus. The system transmits and receives the aforesaid data signal on only one line (38) on the basis of plural sets of serial clock signals (m₁ - m K ), each of the aforesaid apparatuses being assigned one of the plural sets of clock signals to send or receive a corresponding data signal along the data signal line upon receiving the respective set of serial clock signals.

Description: DATA TRANSMISSION SYSTEM This invention relates to a data transmission system for transmitting a remote control signal and data signal, when, for example, a portable video tape recorder (to be hereinafter called VTR) is remotely controlled by exterior additional apparatus, such as a video camera. Conventionally, to control remotely a VTR from a video camera or similar apparatus, control lines are needed (connecting each of the aforesaid apparatuses) as many as the number of the required operating modes. Recently, in order to improve the aforesaid control method, it has been proposed to transmit a remote control signal on one line by means of the assignment of various voltages to respective operating modes, but this method includes defects such as bad resolution, the necessity for a complex encode and decode circuit, and so on. An object of the invention is to provide an efficient data transmission system for transmitting remote control signals and data signals by means of a serial data transmission method whereby a dnta code is transmitted on the basis of a serial clock signal. Accordingly, the present invention provides a data transmission system for sending and receiving data among a plurality of apparatuses on tlie basis of a serial clock signal, comprising a serial clock signal generating means for periodically generating plural sets of serial clock signals (m -mK) a clock signal line for transmitting said plural sets of serial clock signals a plurality of data transmitting/receiving means coupled to said plurality of apparatuses, respectively, for sending and receiving plural sets of serial coded data signals among each other through a data signal line, each of said plurality of data transmitting/ receiving means sending a respective one set of said plural sets of serial coded data signals to said data signal line in accordance with a corresponding one set of said plural sets of serial clock signals (M1 -Mk) . The data transmission system of the preferred embodiment of the invention provides a serial clock signal generating means for generating periodically serial clock signals which consist of n bit serial clock pulse signal units ml, m2 ..... and mK(K being an arbitrary integer), intervals between said serial clock signal units not including any clock signals and being designated tl, t2 ..... and tK. A first data generating means generates coded data pulse signals D1 on the basis of said serial clock signal units ml, a second data generating means generating coded data pulse signal D2 on the basis of said serial clock signal units m2, etc. up to Kth data generating means generating the coded data pulse signals DK. A data transmitting line mixes and transmits said signal D1 provided by the first data generating means, said signals D2 provided by the second data generating means ..... and said signals DK provided by the Kt data generating means, and data receiving means are coupled to said transmission line for receiving said signals, Dl, D2 D ....., and DK on the basis of said clock pulse signal units ml, m2, ....., , and mK. Features and advantages of the invention will be more apparent from the following description of an embodiment thereof when taken in conjunction with the accompanying drawings, in which: Figure 1 is an outline of the remote control system of the preferred embodiment of the invention, which includes a portable video tape recorder, a video camera, a tuner and a wired remote controller; Figure 2 shows a circuit diagram of the data transmission system when using tie apparatus shown in Figure 1; Figure 3 shows waveforms of the serial clock signals and the serial data signals according to the preferred embodiment of the invention; Figure 4 shows similar waveforms to those shown in Figure 3, when using the apparatus shown in Figure 1; ; Figure 5 is the coded form of the serial data signal on the basis of the serial clock signal units m and m6 shown in Figure 4; and Figure 6 is a serial interface circuit diagram for serial data transmission in accordance with the preferred embodiment. Fig. 1 is an outline of a portable VTR and exterior additional apparatuses connected to this VTR. Such apparatuses connected to a portable VTR 1 are a video camera 2, a wired remote controller 3, a tuner4vand so on. Each of them is connected to the VTR l,by cables 10, 11, and 12, and connectors 14, 15, and 16. The video camera 2 is an apparatus which transmits to VTR 1, a video signal converting the objective picture taken by the optical unit in video camera 2 into an electric signal. When picture is taken with a video camera, it is convenient to be able to control VTR 1 by operations on the video camera's side, because, having a video camera in hand, the user directs the video camera to an objective scene. Accordingly, video cameras have conventionally tried to send out such control signals together with the aforesaid video signal to VTR 1 through a cable 10. Also, video camera 2 has customarily sent out an audio signal too from microphone 18 in video camera 2 in addition to the abovementioned signals. As abovementioned, the transmitted signals from video camera 2 to VTR 1 are the control signals, a video signal and an audio signal, but there are the transmitted signals from VTR 1 to video camera 2 to be considered as well. If sending out, for example, the data signals such as a tape counter value and a battery remaining value from VTR 1 to a video camera, the video camera can indicate the values on its body, it is convenient for the user to be able to control all operations, since the user can know information about the VTR 1 on the video camera's' indicator. Video camera indicators have used an electronic view finder consisting of extremely small cathode ray tubes, by which the user confirms the objective picture taken by the video camera. Next, a wired remote controller will be described. This is an apparatus which can control VTR 1 from a place separated a fairly good distance from the VTR 1. There are not, in this case, a video signal and an audio signal sent out from a wired remote controller 3 to VTR 1, but only control signals. However, as it is convenient to indicate tape counter value expressed as a tape travel quantity, and so on as well on the video camera itself, in this case, it is desirable to use a liquid crystal display. Also, the operating switches 8 on the wired remote controller are to be the same as those on the VTR 1. Next, another apparatus, the tuner 4 will be descried, The tuner is an apparatus to obtain the broadcasted video and audio signals by demodulation of on-air-television signal received by antenna. These obtained signals are sent out to VTR 1 through a cable 12 and connector 16. Also, as most tuners have a timer, in this case, the control signals for time setting, recording start, and so on, are sent out from tuner 4 to VTR 1. Furthermore the tuner has a receiver 17 for receiving the infrared rays generated by the wireless remote controller 5, from which the channel selecting command signal, VTR operating command signal, and so on are sent out by pressing the operating buttons 9. However, VTR operating commands from the wireless remote controller, after the controller receives the infrared rays of this command signal by means of receiver 17, need to be converted into the control signal for VTR 1 and sent out to VTR 1. This invention aims at provision of a system for transmitting efficiently the remote control signals and the data signals from each of the abovementioned apparatuses. Fig. 2 shows circuit diagram of an effective example embodiment of the above mentioned remote control system of this invention. In Fig. 2, circuit 40 is a data transmitting and receiving circuit for remote control signals and data signals in VTR 1. VTR 1 needs, besides the aforesaid circuit, a mechanism 25, a battery remaining detecting circuit 32, a video and audio signal processing circuit (not shown in Fig. 2), motor drive and servo circuit (not shown in Fig. 2), and so on. Circuits 50, 60, and 70, are data transmitting and receiving circuits for remote control signals and data signals in video camera 2, wired remote controller, and tuner, respectively. Fig. 2 does not show the optical system and the video and audio processing circuit in the video camera 2, and a demodulator to obtain video and audio signals from on-air-television signal in the tuner 4. Next, each circuit block shown in Fig. 2 will be detailed. The circuit 40 has a serial clock signal generating means 20, a serial data generating and receiving means 22 (to be hereinafter called SDGR means), and an inverter circuit 35. The circuit 50 in the video camera, the circuit 60 in the tuner, the circuit 70 in the wired remote controller 3 have, respectively, SDGR means 46, 54, and 68, and inverter circuits 45, 55, and 65. A serial clock signal shown in Fig. 3-a and Fig. 3-b from the aforesaid serial clock generating means is supplied to a serial clock signal input terminal SCKI on each SDGR means, also serial data signal input terminals SI on SDGR means 22, 46, 54, and 58 are connected with each other by one line 38. A serial data signal output from a serial data signal output terminal of each of circuits 50, 60, 70 and 80, is output on a serial data line through inverter circuits 35, 45, 55 and. 65. The operation of these circuits will be detailed with reference to wave forms of their output signals. As abovementioned, the signals shown in Fig. 3-a and Fig. 3-b are output from a serial clock signal generating means 20. As shown in Fig. 3-a, the serial clock signal consists of a serial clock signal block mO and a no signal interval t generated periodically at intervals of to, and also, a serial clock signal block m0 consisting of n bit serial clock signal units ml, m2 ....., and mK, and no signal intervals tl, t2, ....., and tKl as shown in Fig. 3-b. (Fig. 3-b shows enlargement of a serial clock block mO.) In order to speak generally, Fig. 3-b shows the case wherein the number of the serial clock signal units (to be hereinafter, called SCSU) is K (integer), but the system shown in Fig. 1 deals with the relation among video camera, tuner, wired remote controller, and VTR. In this case, wave forms are shown in Fig. 4, and the serial clock signal shown in Fig. 3-b corresponds to the signal shown in Fig. 4-a. Namely, this serial clock si5nal consists of 8 bit SCSU units m1, in2 and run6. Each SCSU unit ml, m2 , or m6 is assigned a position corresponding to each of these apparatuses. When VTR 1 is controlled by the operation of video camera 2, a serial data signal D1 shown in Fig. 4-b is output from a terminal SO on SDGR means 46, on the basis of a serial clock signal ml. As abovementioned, signal D1 is output into serial data line 38 after inverting to serial data signal D1 by inverter 45. The serial data line 38 is pulled up by resisters 39, 42, 61 and 64 in each apparatus, therefore, the serial data signal on the serial data line 38 becomes "H" level at no signal position and at the position at which the data is "1", as shown in Fig. 4-f. Accordingly, if low level in a signal is "0" and high level in a signal is "1" the code "10101010" of a serial data signal output from a terminal SO on an SDGR means becomes the code "01010101" as a serial data signal on data line 38. Next, for tuner 4, the serial data signal D2, which is output from terminal SO on SDGR means 60 on the basis of SCSU m2, is output into data line 38 through an inverter 55, as shown in Fig. 4-c and Fig. 4-f and also, for a wired remote controller, the serial data signal D3 is output into data line 38 just as in the case of the tuner. (reference to Fig. 4-d and Fig. 4-f.) Serial data signals corresponding to the above mentioned SCSUs m11 m2, and m3 are D1 from a video camera, D2 from a tuner, and D3 from a wired remote controller, respectively. However, SCSUs m4, m5, and m6 are assigned to the serial data signals Dg, D5, and D6 from the VTR 1 to each apparatus, as shown in Fig. 4, that is, the serial data signals D4, D5, and D6 transmit the information of tape counter value indicating tape travel quantity or battery remaining value, from VTR 1 to each of the sub apparatuses. Since tape counter value is shown conventionally by a four figure decimal expression, each decimal number requires conversion from the number's binary value, so that 8 bit serial data signals D5 and D6 corresponding toSCSUs mg, m6 is divided into upper 4 bits and lower 4 bits, as shown in Fig. 5. The upper 4 bit binary code in serial data signal D5 indicates the thousandth digit of the tape counter, the lower 4 bit code in D5 indicates the hundredth digit, the upper 4 bit code in D6 indicates the tenth digit, and the lower 4 bit code in D6 indicates the units digit. However, as VTR 1 needs to out not only a serial data signal of tape counter value, but also a serial data signal of battery remaining value, prior to signals D5 and D6, the VTR sends out serial data signal D4 corresponding to SCSU m4, which indicates whether serial data signals D4 and D5 send out tape counter value or battery remaining value. For example, as shown in Fig. 4, when the code of D4 is "10101010", the next D5 and D6 is a tape counter value. And also, when the code of D4 is "11110000", the next D5 and D6 is a battery remaining value. As the change of counter value during fast forward or fast rewind (of VTR operation) is very rapid and the change of a battery remaining value is very slow, it is efficient to transmit a serial data signal of tape counter value, and once per minute a serial data signal of battery remaining value. Below, the serial data signal input and output of an SDGR means is detailed. An embodied example of an SDGR means is shown in Fig. 5. The SDGR means fundamentally consists of a shift register 74 and the input and output buffer circuits 75, and 76. Each memory circuit (a), (b), (c), (d), (e), (f), (g) and (h) of the shift register 74, which consists of FLIP FLOP circuits, is coupled to a memory circuit 73 which can input and output data in parallel. Though this memory circuit 73 conventionally utiliged its own exclusive IC, recently this circuit utilizes internal RAM (Random Access Memory) of a microcomputer (to be hereinafter called MPU). When a serial data signal is output from the SDGR means, previously the data is latched in memory circuit 73, thereafter this data is sent out to the shift register 74. Data in the shift register 74 is output from terminal so on the basis of a serial clock signal input to a terminal SCK shown in Fig. 6, and also data input to a terminal SI on the SDGR means is taken in the shift register 74 on the basis of this serial clock signal. Data is put in a shift register 74, in order, according to a serial clock signal, until the 8 bit shift register 74 is full, thereafter, data in the shift register 74 is transferred to the memory circuit 73 in parallel. As recent MPUs have all the aforesaid shift register built-in, the operation of the SDGR means can be accomplished by a program in ROM (Read Only Memory) in the MPU. An SDGR means 22, 46, 54, and 68 shown in Fig. 2 consists of the shift register 74 and its buffer circuits 75, 76. The memory circuit 73 corresponds to MPU 23, MPU 48, MPU 56, and MPU 71 in Fig. 2. These MPUs are coupled to the operating buttons 24, 49, and 72, and so, generate the predetermined code by means of pressing the aforesaid operating buttons. This coded signal is sent to an SDGR means, and is converted into a serial data signal by means of an SDGR means, thereafter this serial data signal is output from a terminal SO of the SDGR circuit. A video camera 2, when one of its operating buttons 49 is pressed, transmits the predetermined code for the VTR operation on the basis of SCSU ml, then on SDGR 2 of VTR 1 receives a serial data signal from the video camera on the basis of SCSU ml and sends this received signal to MPU 23, thereafter MPU 48 decodes this received signal and outputs a control signal to the mechanism 25, thereby VTR 1 is operated by video camera 2. Other apparatuses, the tuner and wired remote controller operate the VTR just as in the case of video camera 2. Next, a wireless remote controller 5 which uses a infrared rays will be described. The data signal sent by infrared rays from 2 wireless remote controller 9 is taken in a receiver 17 and is amplified, thereafter this received data signal is decoded and converted into -a serial data signal for VTR operation, and is transmitted to VTR 1. Below the method of detecting a tape counter value and a battery remaining value will be detailed. A rough plan view of the mechanism 25 in VTR 1 is shown in Fig. 2 in a recording or playing condition. A tape 27,-which is pulled out from a tape cassette 26, is wound up by a take-up reel 30 through a guide pole 28 and a rotary head assembly 29. Then, the mechanism is so designed that a magnet 3a is arranged at some distance on the periphery of take-up reel 3G and produces a value for each revolution of the take-up reel 30 in a detector. Accordingly, if a stationary detector 31b (like a hole element) is placed near this magnet 31a, a pulse signal is obtained from detector 31b for each revolution of the reel 30. Provided that this pulse signal is given to MPU 23, MPU 23 counts this pulse signal and sends out the count data to an SDGR means. 22, thereafter the count data is converted into a ser.al data signal D4, D5, and D6 and is output from VTR 1 to each apparatus except VTR 1 on the basis of an SCSU m4, m5 and m6. SDGR means 46 and 68 on video camera 2 and wired remote controller 3 respectively, receive the serial data signal transmitted from VTR 1 on the basis of sCSUs m41 and and m6, and the received data signal is decoded and sent to the indicator by MPU 48. Accordingly, for video camera, this data is indicated on electronic view finder 13 (reference to Fig. 1) and in case of the wired remote controller, on liquid crystal display 7 (reference to Fig. 1) and so, when detecting a battery remaining value, output voltage of battery 34 is given to a battery remaining voltage detector 33, and converted to a degital data signal, thereafter, the data signal output from this detector 33 is taken by PU 23. Though only a serial clock signal line 21 and a serial data signal line 38 are shown in the cable in Fig. 2, each connector and cable of the video camera has the video signal line and an audio signal line besides the above mentioned clock and data lines. As the video and audio signal lines do not relate to this invention, these lines are not shown in Fig. 2. Next, this invention will be further detailed by reference to Fig. 3. Fig. 3 shows wave forms in a general system in which there are SCSU ml, m2 , and mK The number of bits for the SCSU is decided by the number of function of the system, namely the operating mode, thereof. 8 bits is enough for the VTR system shown in Fig. 2 and Fig. 4. In the VTR system, for example, a tuner needs a lot of code for: remote control signal, data signal for selection of television channel, the setting of year, month, week, day and time, the control functions of the VTR, and so on. Next, the method of searching a first SCSU ml for a video camera will be detailed. If the time to connect VTR 1 with connector 14 of video camera 2 is an interval t2, video camera 2 cannot send out a serial data signal at that instant. Accordingly, a serial data signal for the VTR control generated from the video camera must be sent out to VTR 1 on the basis of a serial clock signal ml. Therefore, the SDGR means onthe video camera ignores SCSU m3, m4, m5, and m6 after interval t2 for connecting VTR 1 with a connector 14 and must start sending out a serial data signal on the basis of SCSU ml coming after SCSU m3, m4, m5, and m6. Then, the detection of first SCSU ml after its connection will be explained. SCSU ml is periodically coming after a longest interval t6, so that the SDGR means, provided that a timer 77 is prepared in it, can detect interval t6 because there is no clock signal within a predetermined time set on its timer 77. Therefore, SCSU ml coming after interval t6 can be detected. That is, if the timer 77 in the SDGR means is set to a particular time that is a little longer than the longest interval tnmax of intervals tl, t2, t3, t4 and t5, interval t6 can be detected because interval t6 is longer than the particular time set by the timer 77, and a gate 78 is opend. The abovementioned time relation is as follows: tnmax < t6 Tg 6 T0-(t1+t2+t3+t4+t5+6x8xt0) .. .. (1) wherein to is the period of a serial clock signal. Therefore, the SUGR means can find the first SCSU ml coming after the interval t6. Also, when connector 14 is removed from VTR 1 by accident in a operatiori and again coupled to VTR 1, it is necessary to do the same as the abovementioned searching for the first SCSU ml. The other remote control apparatuses except video camera 1, namely, the tuner and the wired remote controller can utilize the abovementioned method of searching for SCSU, but the tuner needs to find SCSU m2 and the wired remote controller, SCSU m3. Then, the formula (1) is shown in a general form as follows: tnmax < tK = (tl+t2+ ... tK-l n t0) (2) wherein tnmaxs the longest one of tl, t2 , and tK¯l. Also, it is possible to mix the signal such as PH and shown in Fig. 3 at interval tkt since interval tK is rather longer. For example, this signal can be used when VTR 1 should show the other apparatuses that a recording is OK. This information is different from the above mentioned tape counter value and battery remaining value, that is, VTR 1 must transmit a serial data signal of a changeable tape counter value and also, sometimes a battery remaining value in serial data positions D4, D5 and D6, therefore the VTR can not transmit a signal of a constant state of the recording together with a signal of a tape counter value and so on in the same position. Therefore, if the VTR transmits this signal to the other apparatuses at interval tK (t6 in case of Fig. 6), an SDGR means in a remote control apparatus can detect the recording condition according to check levels at intervals of txi wherein, an interval tpL of a signal PL, as shown in Fig. 3, is in the range from tnmax till (TK-to) so that signal PL cannot have an influence on any SCSU, namely this time relation is as follows. tnmax < tPL < tK-t0 ..... (3) This invention uses the interval tK in order to find out the initial SCSU at the time of connecting required apparatus with VTR 1, and decided that interval tk was the longest one of t1, t2 ..... and tK, because this choice simplifies the system. But it is possible to choose anyone of intervals tl, t2 and tK as the longest one, wherein it is desirable that the system he designed on the basis of the chosen interval. While a serial data signal from a remote control apparatus is received and. sent out to MPU 23 in parallel by an SDGR means, therefore MPU 23 decodes a sent data signal and sends a command signal for control of motor 32 and so on to mechanism 25 and for an electric circuit, so that the VTR is operated. As seen from the above, this invention provides a data transmission system for sending and receiving efficiently a remote control signal and a data signal in systems using a portable VTR and its additional apparatus such as video camera, tuner, and wired remote controller and so on, and also this invention has a superior effect in being able to deal with a large scale remote control system through a simplified terminal circuit for receiving and sending a data signal.

Claims: CLAIMS: 1. A data transmission system for sending and receiving data among a plurality of apparatuses on the basis of a serial clock signal, comprising a serial clock signal generating means (20) for periodically generating plural sets of serial clock signals (ml m,) a clock signal line (21) for transmitting said plural sets of serial clock signals, a plurality of data transmitting/receiving means (50, 60, 70) coupled to said plurality OL apparatuses, respectively, for sending and receiving plural sets of serial coded data signals among each other through a data signal line (38), each of said plurality of data transmitting/receiving means sending a respective one set of said plural sets of serial coded data signals to said data signal line in accordance with a corresponding one set of said plural sets of serial clock signals (m1 2. A data transmission system according to claim 1, wherein a time interval between two of said plural sets of serial clock signals (ml - mK) is longer than the longest time interval between two sets of said plural sets of serial clock signals. 3. A data transmission system according to claim 1 or 2, wherein each of said plurality of data transmitting/ receiving means (50, 60, 70) comprises a state recognition unit for recognising each set of said plural sets of serial clock signals and a data transmitter/receiver for sending or receiving said sets of serial coded data signals to or from the other of said plurality of data transmitting/receiving means according to the respective one set of said plural sets of serial clock signals outputted from the particular state recognition unit. 4. A data transmission system according to claim 1, 2 or 3 wherein said serial clock signal generating means further generates a signal for indicating the time interval between two said plural sets of serial clock signals during the time interval between two said plural sets of serial clock signals.

Inventors: MINO, MINEO, NAGASAKI, SAKON, YAMANISHI, KAZUHIRO, YOSHIKAZU, KAGEYAMA
Applicants: MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1982
Main classification: G08C15
IPC codes: G11B20, H04J3, H04Q9, G08C15, H04L5, H04N5, G11B15