JPS61158237A - Data communication method - Google Patents

Abstract

PURPOSE:To improve the time spending efficiency by securing such a system where an optional idle transmission area is selected by a slave device having a transmission request and the transmission is performed through said transmission area. CONSTITUTION:A communication section consisting of the transmission areas P3 and P4 of a master device and the transmission areas P1 and P2 of a slave device is repeated periodically. The number of transmission areas of the slave device is smaller than the number of plural slave devices. For instance, collision occurs between both transmission requests of slave devices I and II at an area P1. Thus the device II changes its transmission area to an area P2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bidirectional data communication method between one master device and a plurality of slave devices.

[Conventional technology]

Recently, in order to enjoy video information, for example, I am using a VTR,
-Construction of a system equipped with a plurality of peripheral devices such as a video camera, a television tuner unit, a timer unit, and an editing machine is underway. In this case, the method of communication of control data such as mode signals and various control signals between the VTR and each peripheral device becomes a problem, but if the method of communication of control data is unified in this system, the same 1ffi, general purpose, and low cost.

One conceivable method for this communication is to use the VTR as a master device and a plurality of peripheral devices as slave devices to perform bidirectional communication. In this case, there is a need to reduce the number of communication lines as much as possible. This is especially true when there are a large number of slave devices.

Therefore, from the perspective of the master device, a method using only two communication lines, a transmission communication line and a reception communication line, or a method in which bidirectional communication can be performed using only one communication line may be considered.

As one of these methods, a manufacturer has already proposed a method in which bidirectional communication can be performed using only one communication line (see international application PCT/JP84/00425).

In other words, in this method, an IM communication interval consisting of a plurality of time-divisionally provided transmission areas for master devices and transmission areas for slave devices is set as one block, and this is periodically repeated. This method is performed only by the master device. In this case, transmission areas for slave devices are provided as many as the number of slave devices.

Even when two transmission lines, one for the master device and one for the slave device, are used, there is only one transmission line from the slave device's perspective, so when performing periodic communication as described above,
After all, transmission from each slave device must be performed in transmission areas provided in a time-division manner.

[Problem to be solved by the invention] However, if a time-division transmission area is provided for every few minutes of multiple slave devices, when the number of slave devices increases, the transmission period of each slave device becomes very large. It has the disadvantage of being long.

In addition, since each slave device does not always send a request for transmission to the master device, if a transmission area is set up for all multiple slave devices as described above, there will be a transmission area that is not used or does not need to be used, and is used inefficiently.

[Means for solving problems]

In this invention, when serial data is bidirectionally communicated between a master device and a plurality of slave devices, a communication section consisting of a plurality of communication areas that do not overlap in time is periodically repeated, and the plurality of communication Each area is set as either the master device's transmission area or the slave device's transmission area, with both areas clearly identifiable, and the number of slave devices' transmission areas being smaller than the number of slave devices. At the same time, the master device manages the time of JM transmission, and the plurality of slave devices perform transmission in any one of the free transmission areas of the plurality of slave devices.

[Effect]

Each slave device does not have a specific transmission area;
A slave device making a transmission request selects any vacant transmission area and transmits in that transmission area.

〔Example〕

FIG. 4 shows an embodiment of a communication system to which the method of the present invention is applied, and in this example, serial data can be communicated bidirectionally through a single communication line. In this example, the master device is a VTR, and the slave devices are, for example, a video camera, a TV tuner unit, an editing machine, and 3 other devices.
This is an example in which more than one video camera is provided, and the configuration of the communication control section on the slave side is the same, so only the video camera is shown in the illustrated example.

That is, in the figure, 0[e indicates that VTR1 (20) is a video camera.

Further, (30) is one data communication line for transmitting control data between the VTR0Φ and the video camera (20) and other slave devices.

The VTR (II) is equipped with a microcomputer (hereinafter referred to as microcomputer) (110) and includes a control unit (11) that controls iW1 communication and other controls, a video circuit and mechanical deck unit (12), and some of the VTR's function keys. (1
3), the VTR%-code display section (14), and the camera (20
) for remote control (hereinafter referred to as remote control).

The video camera (20) also includes a control unit (21) equipped with a microcomputer (210) that performs communication and other controls, a function key part (22) of the camera, and a VTR (I[
Part of the function key (23) for the ll remote control,
For example, it has a display section (24) that can be displayed within the finder. In addition, the motors (25F) (2fiZ) that rotate the focus ring and zoom ring of the pseudo-image lens, respectively, and the iris motor (25T) that controls the opening/closing degree of the aperture drive the motor drive circuits (26F) (26Z) (261). It is connected to the control section (21) via the control section (21).

VTR0 (some of the 11 functions (13) are recorded.

It has function keys such as play, pause, fast forward one rewind, and stop, and when any of these keys is operated, the microcomputer (110) of the control unit (11)
) identifies it, displays it on the display section (14), and supplies necessary control signals to the video circuit and mechanical deck section (12) so that the VTR will be in the mode corresponding to the operated key. be made into

Some of the function keys (23) for the V T Rol remote control on the video camera (20) side also record, play, pause,
It has function keys such as fast forward, rewind, and stop, and when any of the keys is pressed, the
Control data is sent from the camera (20) side to the VTR (Ill) through the communication line (3o), and this is taken into the register of the microcomputer (110) of the control unit (11), and the contents of the data and its Time VTR(lII
The mode of the VTR (IΦ) is determined based on the state of the keys in the function part (13), and the display part (14)
At the same time, the mode is displayed and necessary control signals are supplied to the video circuit and mechanical deck section (12), so that the mode is set. The mode of the VTR001 is determined from the transmission data from the camera (20) and the state of the function keys (13) of the VTR (I'll) in order to prevent erroneous operations. Since there is usually no mode, in this case, the fast forward command is ignored and recording continues.This tells the microcontroller (110) to select which mode the VTR0ω is next based on the combination of remote control signal and function key mode. This can be done by remembering what to do.

In addition, the V T R01 sends back signal data indicating that it is in that mode to the camera (20) side, and the camera (20) side receives it and displays that V T on the display section (24) in the viewfinder. R (101 mode is displayed.

In addition, some of the function keys (15) for the remote control of the camera (20) of the VTR0[Il are focus, iris,
It has keys for zoom, pan, tilt, etc., and when the zoom key is operated, zooming data is transmitted from the V TRO [9 to the camera (20) through the transmission line (30) as described later, and ) control unit (
21) is taken into the register of the microcomputer (210),
Zooming data is supplied to the zoom motor (25Z) through the motor drive circuit (26Z) to perform a zooming operation.

Part of the function key (22) in the camera (20)
If you operate the key, the camera (
20), based on a signal from the microcomputer (210) of the control section (21). For example, if a zoom key is operated on the camera (20), a zooming operation will be performed.

The VTRQ [11171 control unit (11) and the control unit (21) of the video camera (20) are configured as follows. The control unit (21) has exactly the same configuration in other slave devices.

V T R0 (II control unit (11) my: l7 (1
10) and the microcomputer (210) of the control unit (21) of the video camera (20) has an 8-bit shift register (11).
1) and (211) are provided, and these shift registers (111) and (211) each have a serial input terminal SI, a serial output terminal SO, and a clock terminal CK. Also, this shift register (11
1) and (211) are designed to be read and written in the form of parallel data between them and the data bus of the microcomputer.

Also, this shift register (111) and (211”)
The communication controllers (112) and (2) perform serial data loading and serial data reading, respectively.
12). These communication controllers (1
12) and (212) are shift registers (1
11) and (211) Kugata gate switch (113”
) and (213), and a signal G1. G2 and a
1', G2' and shift register (11
Shift clocks CLK and CLK' (one cycle is, for example, 104 μsec) are generated for clocks 1) and 211.

Further, the Urasin controller (112) on the V T Rol side as a master device generates a star bit based on the communication start signal C8 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,
Communication time management is done by master device VT RG11.
Do this only with l.

These communication controllers (112) and (212) can also be realized by a microcomputer.

(115) and (215) are input transistors, (11
6) and (216) are output transistors, and the collectors of the output transistors (116) and (216) are resistors (1
17) and (217) to the power supply terminal, its collector is connected to the communication line (3o), and its emitter is grounded. Also, an output switch (
Shift register (11) via (114) and (214)
1) and (211) are supplied.

Further, the communication line (30) is connected to the input transistor (1i5) and (
215). The emitters of these transistors (115) and (215) are grounded,
The collector is connected to a power supply terminal via resistors (119) and (219), and this collector is connected to a shift register (1) via input switches (113) and (213).
11) and (211).

Therefore, when no data is being transmitted, the communication line (30) is connected to the voltage of the power supply terminal (+5V) via the resistors (117) and (217), and is always at a high level of +5V. becomes.

In the above configuration, V as the master device
T R01 and a video camera as a slave device (20
In this example, as shown in FIG. 3, the bidirectional i1 communication between the two terminals (i1 and 2) is performed in vertical cycles in synchronization with the vertical synchronizing signal VD.

That is, from the perspective of VTR0111 of the master device, the receiving area (transmission area for slave device) P, and P
2, and a section consisting of four areas, transmission areas P3 and P4, is 1ji! This period is set as one signal period, and this period and a certain period of rest period are repeated in a vertical period in synchronization with the vertical synchronization signal VD. In this case, the transmission area for the slave device is P
There are two, L and P2, which is less than the number of slave devices. Transmissions from slave devices are from areas P1 and P2 as described later.
The event will be held using the vacant area.

Each area P1. P2. P3. The first bit of P4 is used as a start bit, which is obtained only from V TRO (R) as the master device, and based on this, transmission and reception between the master device and slave devices is performed.In other words, the communication controller From (112), four start bits SB for one communication section are generated repeatedly at a constant cycle.

Further, 8-bit serial data Do-D7 is transmitted in each of the transmission areas P1 to P4, and one word is composed of the 8-bit data Do=Dv. In this case, since there are four communication areas in one communication section, four words of data are exchanged within one vertical period TF. In this way, the number of words and the number of bits within the communication zone are fixed, so the length of the communication section is constant. Therefore, the length of the pause section is also constant.

1i! Transmission and reception within the communication section is performed as follows.

First, transmission from the master device will be explained.

A communication start signal C3 (FIG. 5A) is generated from the microcomputer (110) of the master device, and is supplied to the communication controller (112).

This communication start signal C3keif! It is always "1" and falls to "0" when requesting to start an IM communication. In this example, the signal falls four times in one vertical period TF. Communication controller (11
In 2), when this communication start request is made, for example, the signal C
The start bit SB becomes "1" for a period of 1 bit with a specified length of 104 μsec from the falling edge of 8 (Figure 5B)
is obtained, which is the output 9 (116) (D
The signal is supplied to the base and is supplied to the communication line (30) to which the collector is connected as a "0" signal with inverted polarity.

Further, following this start bit SB, the communication controller (112) sends eight clock pulses C! with a clock period of 104 μsec! , K (FIG. 5C) are obtained and supplied to the clock terminal of the shift register (111). In addition, the control signal G1 of the output switch (114)
(D in FIG. 5) becomes "1" during the period of these eight clock pulses CLK, and the output switch (114) is turned on.

The microcomputer (110) uses a shift register (
Since the transmission data DTi (FIG. 5F) is preset in the shift register (111), the 8-bit transmission data DTi (FIG. 5F) is read out from the shift register (111) by these eight clock pulses CLK, and this is sent to the output switch. (1
14) and the output transistor (116) through the ltl
It is supplied to the signal line (30). Figure 5 G shows this JM Shinko Union (
30) This is the state of the above signal.

When this 8-bit transmission data DT1 is sent out, the switch (114) is turned off, and therefore the communication line (30)
is pulled up to "1". This "1" period continues for 2.5 to 5 bits. This period of 2.5 to 5 bits becomes an end bit (see FIGS. 3 and 5G).

Normally, the end focus is about 2 bits, but in this example, all the processing is done by the microcomputer's software, so the stop bit is longer than usual, and the communication data is taken into another RAM of the microcomputer. Processing time for storing data is secured.

In this way, the transmission data transmitted from the master side in this transmission area is transmitted to the slave device, such as a video camera (
20) side input transistor (215). Then, at the start bit SB, this input transistor (215) is turned off, and its collector output rises to "1". Then, this is detected by the communication controller (212) and the input port isochi (213) is detected.
) control signal 61' (FIG. 5 I) becomes "1" and eight clock pulses CIJ' with a period of 104 μsec are generated.
(K in FIG. 5) is obtained, the switch (2] 3) is turned on, and the clock pulse CLK' is supplied to the clock terminal of the shift register (211). Therefore, the transmission data DT1 from the VTR (101) is captured into this shift register (211).The captured data is then transferred and stored in the RAM of the microcomputer (210) during the stop bit period. , data D T 2 sent from the video camera (20) to VT R001 is transferred to this shift register (211>
is set to

At this time, the data DTI is also taken in by the other slave devices at the same time, but whether or not the data DTI is used in that slave device is determined by reading its contents by each microcomputer.

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

Now, when there is a transmission request from the video camera (2o) and the transmission request signal DM is supplied to the communication controller (212), the video camera (2o) enters the transmission standby state, and the shift register (211,) Data DT2 (right side of FIG. 5H) is stored.

In this state, a start pit SB is generated from the communication controller (112) of the VTR0... at the beginning of area P1, and this is transmitted via the transistor (116) to the communication line (
30) and transmitted to the video camera (20). Then, as shown on the right side of Figure 5G, the iM signal line (30
) is in the state of "0" for one bit period. Therefore, the input transistor (21) of the video camera (20)
5) is turned off, and its collector output becomes "1".

The im communication controller (212) detects this and outputs the control signal G2' (Fig. 5 J) of the output switch (214).
becomes "1", this output switch (214) is turned on, and eight clock pulses C1. ' is generated during the period of "1" of this signal 02', and this is supplied to the clock terminal of the shift register (211).

Therefore, the data D T 2 is transferred to this shift register (
211 ) (see FIG. 5H) and supplied to the communication line (3o) via the output transistor (216).

On the other hand, V T R (l[Il side communication controller (
112) outputs the start bit SR, and then the control signal G2 (Fig. 5E) of the input switch (113) becomes "1".
”, this input switch (113) turns on, and eight clock pulses CLK (Fig. 5C)
is obtained during the period in which the signal G2 is ".1".

Therefore, the data D T 2 transmitted from the video camera (20) is supplied to the shift register (111) via the input transistor (115) and the switch (113), and is input to this shift register (111') by the clock pulse CIJ. It is captured.

)tll of the end bit of this route area P1
n31, the data is transferred to the RAM of the microcomputer (110) and stored.

The above is a case where the first area P1 of the communication section is not used as a transmission area for other slave devices, but if this area P1 is also used as a transmission area for other slave devices, the following will occur. In this way, area collision is avoided and the transmission area of one slave device is switched to the next area P2.

FIG. 1 is a flowchart for this purpose, and a program according to this flowchart is executed by a microcomputer in a control section of each slave device.

That is, when a start bit is transmitted from the master device to each slave device at the beginning of area P1, the slave device that has made the transmission request receives the data to be sent as described above. ] is sent to the signal line (30) (step [101]). At this time, the data sent to the imm wire 30) and the status of the communication line (30) are checked bit by bit (step (102)).

In other words, the communication line (30) is configured such that the transmitted data is
If the data is "0", the output transistor (216) is off, so the voltage is 5V, and if the data is "1", the output transistor (216) is turned on, so the voltage should be Ov.

However, when transmission data is being sent from multiple slave devices, when the data bit from one of the slave devices becomes "1", its output transistor (216>
is turned on, so it goes down to ov regardless of the data of other slave devices.

Therefore, by detecting that the communication line (30) has become Ov even though the bit of the sent data is "0", the data sent out and the data transmitted on the communication line (30) can be Differences are detected (step (10)
3]). At the same time, it is detected that another slave device is transmitting data in this area P1.

As can be seen from the above, when a collision occurs in which two or more slave devices perform transmission in the same transmission area, the transmission data bits DO to D7 are the earliest.
A slave device that becomes in a state of transmitting "1" is given priority, and that area is taken as the transmission area of that slave device. In the slave device where it is detected that the transmission data differs from the data communicated on the communication line (30) for each bit, all subsequent bits are set to "0" and the area P1 becomes the transmission area. This prevents communication errors from occurring in the transmission data of slave devices defined as .

In this way, in the sleep device that could not transmit in area P1, transmission data is sent out again by the start bit SB that arrives at the beginning of area P2 (step (104)). Then, whether this area P2 is vacant or not is checked bit by bit in steps (105) and [106] in the same manner as described above,
If it is vacant, this area P2 is selected as the transmission area for that slave device. If it is not vacant, it is determined again in the next cycle whether or not area P1 is vacant, and the above operations are repeated until a vacant area is detected.

Figure 2 schematically shows the above operation. In this example, the slave device ■ (for example, a tuner) and the slave device ■ (for example, an editing machine) collide in transmission requests in area P1, and the slave device ■ edits. This indicates that the aircraft has changed its transmission area to area P2.

In addition, the check for each bit is performed using the shift register (211).
This can be easily achieved by increasing the number of stages to nine. Practically speaking, the currently used shift register built into a 4-bit microcomputer has nine stages, so it can be used as is.

In the idle period after the communication period consisting of areas P1 to P4 as described above, the VTR0Φ and video camera (20
) and other slave devices perform processing based on the received data contents, and also perform other tasks by time-sharing processing.

Thereafter, in the same way, communication sections in which one block includes transmissions from the VTR0I 11 and transmissions from slave devices such as the camera (20) are periodically repeated with pause sections in between. In this example, the start bit is generated only from the master device, and as a result, the master device manages the time, so areas P1 to P4 can be reliably determined, and communication areas and pause The interval is reliably distinguished.

As described above, since communication is performed periodically, even if a communication is missed or a communication error is made, the correct content can be restored immediately.

In addition, in the above example, communication and other tasks can all be done with a single chip microcontroller without using an expensive interface, so it is possible to perform two-way digital communication using an inexpensive consumer LSI and one iWU signal line. Data IM communication can be realized.

Also, since communication is synchronized on the master device side, even if multiple tasks other than communication need to be processed in a time-sharing manner, there is no possibility that one task will stop midway through. will disappear.

Note that the generation of the start bit SR and the generation of clock pulses in the communication controller (112), as well as the detection of the start bit and the generation of clock pulses in the communication controller (212), may be performed by microcomputer control. It is also possible to provide hardware separate from the microcomputer, as shown in the figure below.

Furthermore, although the above example is a special example in which only one communication line is required, the present invention is also applicable to cases where two lines, a transmission line and a reception line, are provided between a master device and multiple slave devices from the perspective of the master device. Of course it is possible.

Also, in the above example, the check to see if the transmission area is free was done for each bit, but this is for 1 word (8
Of course, it is also possible to perform the process for each bit.

〔Effect of the invention〕

As described above, in this invention, transmission from a slave device is performed using any vacant area among a plurality of time division areas, so the number of time division areas may be less than the number of slave devices. In addition, there is less unused area, which improves usage efficiency. Furthermore, when communication is performed at a fixed period, for example, a vertical period, the length of the communication section does not become unnecessarily long, and therefore, sufficient time can be taken for tasks other than communication during the pause period.

[Brief explanation of the drawing]

Figure 1 is a flowchart for explaining this invention, Figure 2 is a flowchart for explaining the invention;
3 is a time chart for explaining the invention in detail, FIG. 4 is a block diagram of an embodiment of a communication system implementing the invention, and FIG. 5 is a diagram schematically showing its operation. is a diagram for explaining the same. Ol is a VTR as a master device, (20) is a video camera as one of multiple slave devices, Pl, P2
is the slave device transmission area, Pl. P4 is a master device transmission area, and (3o) is a communication line.

Claims (1)

[Claims] When bidirectionally communicating serial data between a master device and multiple slave devices, a communication section consisting of multiple communication areas that do not overlap in time is periodically repeated, and each of the multiple communication areas is Set either the transmission area of the master device or the transmission area of the slave device in a state where both areas can be identified, and the number of transmission areas of the slave device is smaller than the number of the multiple slave devices, and the above. A data communication method in which a master device manages communication time, and the plurality of slave devices transmit data in any one of the available transmission areas of the plurality of slave devices.