JP3148583B2 - Centralized control device for cooling storage - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for centrally managing the operation of cooling storages such as a plurality of prefabricated refrigerators / refrigerators and showcases.

[0002]

2. Description of the Related Art Conventionally, a plurality of prefabricated refrigerators / refrigerators have been installed in supermarkets and hotels, etc. Conventionally, each prefabricated refrigerator / refrigerator has a control device comprising a temperature controller and a defrost timer. At present, it is controlled individually. Therefore, various setting operations such as the temperature and the defrosting time of each prefabricated refrigerator / refrigerator must be individually performed at the place where the prefabricated refrigerator / refrigerator is installed. Therefore, there is a problem that the operation becomes extremely complicated when the setting is changed depending on the season or weather.

For this reason, for example, Japanese Patent Application Laid-Open No.
In the official gazette (F25D21 / 06), a control device for a plurality of showcases is connected to a centralized control device constituted by a microcomputer via a communication line, and various setting operations for each showcase are performed by the centralized control device. In addition, the configuration is such that data relating to the operating state of the showcase is collected in a centralized management device and managed collectively.

[0004]

Here, when an abnormality such as abnormally high or low temperature occurs in each of the prefabricated refrigerators / refrigerators, each controller usually detects the abnormality and issues an alarm. Occurs when the person is absent,
In addition, with respect to abnormalities that have returned to normal, the alarm history of such abnormalities is usually stored in a memory or the like, and the alarm history is displayed by an operation performed by an administrator during maintenance or the like. Conventionally, a special switch for displaying the alarm history is provided for each prefabricated refrigeration unit.
Since it is provided in the control device of the refrigerator, the number of components of the control device is increased, which causes inconveniences such as a rise in cost, a hindrance to downsizing, and a deterioration in operability.

Further, when a three-phase power supply for supplying power to a compressor of a prefabricated refrigerator / refrigerator is connected in reverse phase, the compressor is damaged by detecting the reverse phase connection in order to damage the compressor. However, it was not clear to the administrator why the compressor had stopped, and it was not possible to take prompt and appropriate measures to damage the stored items. There was also a problem that would occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional technical problem, and has an improved usability in a centralized management device for collectively managing the operation state of a cooling storage, and The purpose is to reduce costs.

[0007]

According to a first aspect of the present invention, there is provided a centralized management device for managing the operating states of a plurality of cooling storages collectively. A terminal-side control unit is provided in each cooling storage unit, controls operation of each cooling storage unit, and exchanges data with the central management unit. The central management unit and the terminal-side control unit perform reception preparation. Before output is set, the output terminal is set to a fixed logic level, and when reception preparation is completed, the output terminal is set to the opposite logic level. The data transmission is executed by recognizing the state of the side.

A centralized management device according to a second aspect of the present invention collectively manages the operation states of a plurality of cooling storages. The centralized management device is provided in the centralized management device and each cooling storage, A terminal-side control device that executes operation control of each cooling storage and exchanges data with the central control device, and both the central control device and the terminal-side control device set the synchronous clock terminal to the input mode. At the same time, the general-purpose input / output terminal is connected to the synchronous clock terminal on the transmission side, and a synchronous clock signal is output from the general-purpose input / output terminal to execute data transmission / reception.

[0009]

[0010]

[0011]

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a centralized management device 1 according to the present invention.
FIG. 2 is a perspective view (appearance) of the terminal-side control device 3. The centralized management device 1 of the present invention collectively manages the operating state of, for example, a plurality of prefabricated freezer / refrigerators (cooling storages) (not shown), and includes a centralized management device 2 configured by an ordinary personal computer or the like. When,
It is composed of a plurality of terminal-side control devices 3 provided in each prefabricated refrigerator / refrigerator.

Each terminal-side control device 3 is composed of a general-purpose microcomputer 4, and a connection port 6 of the microcomputer 4 is connected to a communication line (communication line) 7.
(Composed of three communication lines 7A, 7B and 7C as will be described later), a bus line (communication line) from the central management unit 2
8 is connected. The general-purpose input / output terminals P1 to P5 of the microcomputer 4 are connected to a reverse phase detector 11, a temperature sensor 12, an operation / display board 13, an electromagnetic valve 14, and a compressor 16, respectively, as reverse phase detecting means. I have. A mode changeover switch 17 is connected to general-purpose input / output terminals P6 and P7 of the microcomputer 4.

The compressor 16 includes a cooler (not shown) provided in a prefabricated refrigerator / refrigerator, and the electromagnetic valve 1.
4. A well-known refrigeration cycle is constituted together with the condenser provided outside the refrigerator. The reverse phase detector 11 detects a reverse phase connection of a three-phase AC power supply connected to the compressor 16, and the temperature sensor 12 detects a temperature inside the prefabricated refrigerator / refrigerator.

The operation / display board 13 is provided with a display 21 composed of, for example, a 4-digit 7-segment LED as display means, a display changeover switch 22 and a forced defrosting switch 23 for the cooler. There is provided a reverse-phase alarm 24 composed of a light source and a lamp, and a communication status LED 26 as a light emitting means composed of one LED.
The communication status LED 26 is attached to the outer surface of the terminal-side control device 3 or is located at a remote position (such as a control room).
Attached to. In addition, a temperature control volume (not shown) for setting temperature is installed inside.

Next, the operation will be described. Each prefab frozen
The settings such as the refrigerator internal temperature are set by the temperature control volume. Now, assuming that the microcomputer 4 of the terminal side control device 3 is set to the single operation mode by operating the mode changeover switch 17, the microcomputer 4 detects the data set by itself and the temperature sensor 12 as described above. Based on the internal temperature, the electromagnetic valve 14 is opened and closed so that the internal temperature approaches the set temperature.

The solenoid valve 14 controls the flow of refrigerant into the cooler. When the solenoid valve 14 is opened, the suction side pressure of the compressor 16 increases, and a low-pressure switch (not shown) is closed to compress the refrigerant. The machine 16 is activated. The refrigerant discharged from the compressor 16 is condensed in the condenser, decompressed by a decompression device (not shown), flows into the cooler, and evaporates.
The interior of the prefabricated refrigerator / refrigerator is cooled by the endothermic effect generated at this time.

When the internal temperature drops to the set temperature due to the cooling, the microcomputer 4 sets the temperature sensor 12
, The solenoid valve 14 is closed. When the solenoid valve 14 is closed, the flow of refrigerant into the cooler stops, and the compressor 1
The suction side pressure at 6 drops, the low pressure switch opens, and the compressor 16 stops. By the operation as described above, the temperature inside the refrigerator of the prefabricated freezer / refrigerator is maintained at the set predetermined refrigeration or freezing temperature (set temperature). Further, the microcomputer 4 executes the defrosting of the cooler at a preset predetermined defrosting timing (at a fixed time interval). Further, the microcomputer 4 normally displays the internal temperature detected by the temperature sensor 12 on the display 21, but the operation (push) of the display changeover switch 22 switches the set temperature and the like to the display 21. indicate.

When the forced defrost switch 23 is pressed, the microcomputer 4 forcibly starts the defrosting of the cooler regardless of the defrosting timing. by this,
Defrosting can be reliably performed in a season with much frost formation, and the operation of the defrost heater and the like can be easily checked. Next, the microcomputer 4 determines various abnormalities (high temperature, low temperature abnormalities, etc.) occurring in the prefabricated refrigerator / refrigerator, and when such abnormalities occur due to a failure of the device (the compressor 16 or the temperature sensor 12), the display 4 At 21, the occurrence of the alarm is displayed, and the alarm data is stored in the memory M as storage means. When a plurality of alarms are generated, all alarm data is stored. Such an alarm display allows the administrator to quickly take measures such as repair.

At this time, for example, when the administrator is absent and the alarm display disappears due to the abnormality being restored to normal without noticing the alarm display, the display changeover switch 22 is used at the time of maintenance or the like. When the forcible defrost switch 23 is pressed while pressing, the microcomputer 4 displays the past alarm data stored in the memory M on the display 21. In this case, if there are a plurality of alarm data, the next alarm data is sequentially displayed on the display 21 by pressing the forced defrost switch 23 while pressing the display changeover switch 22 as it is.

In this way, the past alarm history can be displayed on the terminal side control device 3 and the display changeover switch 22 and the forced defrosting switch 23 are also used, so that a special alarm history display switch is provided. It becomes unnecessary, cost can be reduced, and the overall size of the terminal-side control device 3 can be reduced while maintaining usability. Further, the reverse phase alarm operation by the microcomputer 4 is shown in FIG.
This will be described with reference to the flowchart of FIG. The microcomputer 4 monitors whether or not the three-phase AC power supply connected to the compressor 16 is connected in reverse phase at step S1 in FIG. Then, the process proceeds from step S1 to step S2 to execute the above-described normal control.

Next, when a three-phase AC power supply is connected to the compressor 16 in reverse phase, the microcomputer 4
In step S1, the flow proceeds to step S3 to stop the compressor 16 by cutting off the power to the compressor 16, and in step S4, turns on the negative phase alarm 24 to display a negative phase alarm. I do. As a result, it is possible to prevent the compressor 16 (load) from being damaged due to the reverse-phase connection, and it is possible to accurately notify the administrator of the occurrence of the reverse-phase connection, thereby achieving quick and accurate operation. The treatment can be realized.

Here, the microcomputer 4 of the terminal-side control device 3 enters the centralized management mode by operating the mode changeover switch 17. Various setting values such as the internal temperature and defrosting timing of each prefabricated refrigerator / refrigerator can be collectively set by the central management device 2, and the data is controlled by the bus line 8 and the communication line 7 at each terminal side. It is transmitted to the device 3. The microcomputer 4 of the terminal-side control device 3 receives the transmitted data in the state of the centralized management mode described above, updates the data set by itself as described above, and executes the control operation.

In the centralized control mode, the microcomputer 4 transmits control data (temperature data and alarm data) as described above to the communication line 7 and the bus line 8.
Is transmitted to the central management device 2. The central management device 2 collects and manages the data on the operation state transmitted from the terminal-side control device 3. Thereby, the central management device 2
, Centralized management of the operating state of a plurality of prefabricated refrigerators / refrigerators can be performed.

Next, the transmission / reception display operation by the microcomputer 4 of the terminal side control device 3 will be described with reference to the flowchart of FIG. The microcomputer 4 of the terminal-side control device 3 sets a transmission start flag when transmitting the data on the operation state to the central management device 2. Then, it is determined whether or not the transmission start flag is set in step S5. If the transmission start flag is set, the process proceeds to step S20 to determine whether or not the LED extinguishing flag is set.
Here, assuming that the microcomputer has been reset, the microcomputer 4 proceeds to step S6 and proceeds to step S6.
6 is turned on.

Next, in step S7, a 0.5 second (s) timer which the microcomputer 4 has as a function is counted, and in step S8, it is determined whether or not the transmission end flag is set. Now, assuming that the data transmission has not ended, the transmission end flag has been reset,
The microcomputer 4 proceeds to step S9 to determine whether or not the counting of the 0.5 second timer is completed, and if not, returns to step S5. When the 0.5 second timer counts up, the process proceeds to step S22, where 0.5
The second timer is reset, and it is determined in step S23 whether the LED extinguishing flag is set. Here, since it has been reset, the process proceeds to step S24, sets the LED extinguishing flag, and returns to step S5.

Then, from step S5 to step S20
Since the LED extinguishing flag is set here, the process proceeds to step S21 to extinguish the communication status LED. Next, a 0.5 second timer is counted in step S7, and then it is determined in step S8 whether or not the transmission end flag has been set. Assuming that the data transmission has not been completed yet, the microcomputer 4 proceeds to step S9.
To determine whether or not the counting of the 0.5 second timer is completed. If not, the process returns to step S5. And
When the 0.5 second timer counts up, step S22
And resets the 0.5 second timer to step S23.
It is determined whether or not the LED extinguishing flag is set. Here, since it is set, the process proceeds to step S25, the LED extinguishing flag is reset, and the process returns to step S5.

By repeating the above, the microcomputer 4 blinks the communication status LED 26 every 0.5 seconds (the first light emission state) during transmission. When the transmission is completed, the microcomputer 4 sets the transmission end flag. Therefore, the process proceeds from step S8 to step S10 to reset the transmission start flag, and proceeds to step S11 to turn off the communication status LED 26.

Next, the microcomputer 4 of the terminal-side control device 3 sets a reception start flag when receiving data relating to settings from the central management device 2. Then, it is determined in step S12 whether or not the reception start flag is set. If the flag is set, the process proceeds to step S26 to determine whether or not the LED extinguishing flag is set. Here, assuming that the microcomputer has been reset, the microcomputer 4 proceeds to step S13 and sets the communication state L
The ED 26 is turned on.

Next, in step S14, the one-second (s) timer which the microcomputer 4 has as a function is counted, and in step S15, it is determined whether or not the reception end flag is set. Now, assuming that data reception has not ended, the reception end flag has been reset,
The microcomputer 4 proceeds to step S16 to determine whether or not the counting of the one-second timer is completed, and if not, returns to step S5. When the one-second timer counts up, the process proceeds to step S28, where the one-second timer is reset, and it is determined in step S29 whether the LED extinguishing flag is set. Here, since it has been reset, the process proceeds to step S30, sets the LED extinguishing flag, and returns to step S5.

Then, from step S12 to step S2
The process proceeds to step S6. Since the LED extinguishing flag is set here, the process proceeds to step S27 to extinguish the communication status LED. Next, the one-second timer is counted in step S14, and then it is determined in step S15 whether the reception end flag has been set. Assuming that the data reception has not yet been completed, the microcomputer 4 proceeds to step S
Proceeding to 16, it is determined whether or not the counting of the one-second timer has been completed. If not, the process returns to step S5. And 1
When the second timer counts up, the process proceeds to step S28, where the 1 second timer is reset, and the LED is set in step S29.
It is determined whether the light-off flag is set. Here, since it is set, the process proceeds to step S31 and the LED
The light-off flag is reset, and the process returns to step S5.

By repeating the above, the microcomputer 4 makes the communication status LED 26 blink every other second (second light emission state) during reception. When the reception is completed, the microcomputer 4 sets the reception end flag.
Proceeding from step S15 to step S17, the reception start flag is reset, and proceeding to step S11, the communication state L
The ED 26 is turned off.

As described above, the microcomputer 4 of the terminal-side control device 3 controls the communication status LED 2 during data transmission.
6 flashes every 0.5 seconds, and flashes every second during data reception, so that the data communication state (transmission / reception) of the terminal side control device 3 can be easily determined, and Discovery can be performed quickly, and reliability can be improved and early treatment can be realized.

Next, an actual data transmission method between the central management device 2 and the terminal-side control device 3 will be described with reference to FIGS. FIG. 5 shows an internal block diagram of the microcomputer constituting the central management device 2 and the microcomputer 4 of the terminal side control device 3. Each microcomputer includes frequency dividers b1 and b2, synchronization circuits c1 and c2, transmission buffers d1 and e2, and reception buffers e1 and d2.
The frequency dividers b1 and b2 are connected to the input terminals XIN and the synchronous circuits c1 and
c2 is connected to the clock terminal SCLK and the transmission buffers d1 and e
2 is connected to the data output terminal SOUT and the reception buffer e
1 and d2 are connected to the data input terminal SIN, respectively.

An oscillation element (not shown) is connected to XIN, and clock terminals SCLK are connected to each other via a communication line 7A. The data output terminal SOUT of the microcomputer of the central management unit 2 is connected to the data input terminal SIN of the microcomputer 4 via a communication line 7B, and the data input terminal SIN of the microcomputer of the central management unit 2 is connected via a communication line 7C. It is connected to the data output terminal SOUT of the microcomputer 4.

The general-purpose input / output terminal PK of the microcomputer of the central management unit 2 is connected to the clock terminal SCLK. Further, each microcomputer has a terminal a1,
When the switch signal of “H” is input to a2, the synchronization circuit c1,
The clock source of c2 is set to the internal clock mode in which the signal from the input terminal XIN is frequency-divided by the frequency dividers b1 and b2, and when the "L" signal is input to the terminals a1 and a2, the clock terminal SCLK is input. Mode and synchronous circuits c1 and c
The second clock source is set to the external clock mode in which the signal is input from the clock terminal SCLK.

In the present invention, an "L" signal is input to terminals a1 and a2 of both microcomputers, and a clock terminal SC is input.
LK is set to the input mode, and the external clock mode in which the clock source of the synchronization circuits c1 and c2 is a signal input from the clock terminal SCLK. Further, the general-purpose input / output terminal PK of the central management device 2 outputs a synchronous clock signal created by software.

Now, assuming a case where data is transmitted from the central management device 2 (transmission side) to the terminal side control device 3 (reception side), the microcomputer 4 of the terminal side control device 3 is not ready for reception. (Q1 in FIG. 6) switches the data output terminal SOUT to a general-purpose input / output terminal, and outputs an "L" reception disabled signal ("L" logical level). The microcomputer of the central management device 2 normally switches the data input terminal SIN to a general-purpose input / output terminal, and monitors the state of the data output terminal SOUT of the microcomputer 4.

When the microcomputer 4 is ready for reception, the microcomputer 4 outputs a "H" reception permission signal ("H" logic level) from the data output terminal SOUT at Q2 in FIG. Then, the microcomputer 4 switches the data output terminal SOUT to the original synchronizing signal output terminal, and waits for a clock signal and a data output signal to be output from the microcomputer of the central management device 2.

On the other hand, the microcomputer of the central management unit 2 informs the data output terminal SOUT of the microcomputer 4 of the terminal-side control device 3 that the reception enable signal of "H" (logic level of "H") has been output. After detecting at the input terminal SIN, the microcomputer 4 secures a time Q3 sufficient to switch the data output terminal SOUT from the general-purpose input / output terminal to the synchronization signal output terminal, and then executes the software from the clock output terminal SCLK as described above. Output the created synchronous clock signal.

With this synchronous clock signal, the data of the transmission buffer d1 of the microcomputer of the central management unit 2 is transmitted from the data output terminal SOUT to the data input terminal SIN of the microcomputer 4 (the reception buffer d).
2), the data in the transmission buffer e2 of the microcomputer 4 is sent from the data output terminal SOUT to the data input terminal SIN of the microcomputer of the central control unit.
(Stored in the reception buffer e1).

Thus, the transfer of data between the central management device 2 and the terminal-side control device 3 is completed. After the completion of the data transfer, the data input terminal SIN of the microcomputer of the central management unit 2 and the data output terminal SOUT of the microcomputer 4 are switched to general-purpose input / output terminals to prepare for data transfer. The same applies to the case where the receiving side and the transmitting side are reversed.

As described above, in the present invention, the microcomputer of the central management unit 2 and the microcomputer 4 of the terminal-side control unit 3 use the data output terminal SOUT as a general-purpose input / output terminal before the reception preparation is completed. When the reception is ready, the logic level of SOUT is set to “H”, and the logic level of the data output terminal SOUT on the receiving side is monitored at the data input terminal SIN.
Since data transmission is performed by recognizing the state of the receiving side, as shown in FIG. 7, a terminal SRDY and a communication line 7D for transmitting a reception preparation end signal which are conventionally required as shown in FIG.
Becomes unnecessary, and the number of communication lines between the central management device 2 and the terminal-side control device 3 can be reduced, so that labor and simplification of connection and maintenance can be reduced, and the failure rate can be reduced.

The microcomputer of the central management device 2 and the microcomputer 4 of the terminal-side control device 3 both set the clock terminal SCLK in the input mode, and the general-purpose input / output terminal PK is connected to the clock terminal SCLK on the transmission side. Connected, and a synchronous clock signal is output from the general-purpose input / output terminal PK to transmit and receive data. Therefore, compared to the case where an external oscillation element is used as in the related art, software on the transmission side is used. Thus, the synchronization clock can be freely selected. Therefore, an element having a low response speed such as a photocoupler can be used on a communication line, and the degree of freedom in circuit design can be increased.

In the above embodiment, the case where data communication is directly performed between the terminal-side control device 3 and the central management device 2 has been described. A communication device (included in the central management device 2) is interposed between the communication devices (communication line 7), and the terminal-side control device 3 performs the above-described data communication with the communication device. good. Further, in the embodiment, the present invention is applied to a prefabricated refrigerator / refrigerator. However, the present invention is not limited thereto, and the present invention is also effective to a low-temperature showcase or a commercial refrigerator.

[0046]

As described above in detail, according to the first aspect of the present invention, data is exchanged between the terminal-side control device for executing the operation control of each cooling storage and the central management device. The centralized management of the operation state of a plurality of cooling storages can be performed at the time. In particular, the central management unit and the terminal-side control device set the output terminal to a fixed logic level before the reception preparation is completed, and set the output terminal to the opposite logic level when the reception preparation is completed, and set the input terminal to the input terminal. The data transmission is performed by monitoring the logic level of the output terminal on the receiving side and recognizing the state of the receiving side. By reducing the number of communication wires between the management device and the terminal-side control device, labor and simplification of connection and maintenance can be reduced, and the failure rate can be reduced.

The centralized management device according to the second aspect of the present invention exchanges data between the terminal-side control device that executes operation control of each cooling storage and the centralized management device. Centralized management of the operating state of the storage can be performed. In particular, both the central control device and the terminal-side control device set the synchronous clock terminal to the input mode,
The general-purpose input / output terminal is connected to the synchronous clock terminal on the transmission side, and a synchronous clock signal is output from this general-purpose input / output terminal to execute data transmission / reception. As compared with the case of using, it is possible to freely select a synchronization clock by the transmission side, and it is possible to use elements with a slow response speed on the communication line, thereby increasing the degree of freedom in circuit design. be able to.

[0048]

[0049]

[0050]

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a centralized management device of the present invention.

FIG. 2 is a perspective view of a terminal-side control device.

FIG. 3 is a flowchart showing a program of a microcomputer of the terminal-side control device.

FIG. 4 is a flowchart showing a program of a microcomputer of the terminal-side control device.

FIG. 5 is a block diagram showing an internal configuration of a microcomputer of a central management device and a terminal-side control device.

FIG. 6 is a diagram illustrating a data transmission method between a central management device and a terminal-side control device.

FIG. 7 is a diagram illustrating a conventional data transmission method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Central management device 2 Central management device 3 Terminal side control device 4 Microcomputer 7 Communication line 11 Negative phase detector 21 Display 22 Display changeover switch 23 Forced defrost switch 24 Negative phase alarm 26 Communication status LED M memory

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuyuki Kobashi 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Hiroyuki Kurihara 2-5-5 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (72) Inventor Takeshi Aoki 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A 5-2722863 (JP, A) JP-A-5-45043 (JP, A) JP-A-63-188720 (JP, A) JP-A-5-75672 (JP, A) JP-A-4-314253 (JP, A) JP-A-4-148387 ( JP, A) Japanese Utility Model 1-78889 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F25D 23/00 301 F25D 11/00 101

Claims (2)

(57) [Claims] 1. A centralized control apparatus to collectively manage the driving condition of the plurality of cooling storages, the central control device includes a central management unit, provided in each cooling storage, and executes operation control of each cooling storages Along with
A terminal-side control device that transmits and receives data to and from the central management device, and the central management device and the terminal-side control device have their output terminals at a fixed logic level before reception preparation is completed, When the reception preparation is completed, the output terminal is set to the opposite logic level, the input terminal monitors the logic level of the output terminal on the reception side, and recognizes the state of the reception side to execute data transmission. A centralized control device for a cooling storage. 2. A centralized management device for collectively managing the operation states of a plurality of cooling storages, wherein the centralized management device is provided in each of the cooling storages and controls the operation of each cooling storage. Along with
A terminal-side control device for transmitting and receiving data to and from the central control device, wherein the central control device and the terminal-side control device both have a synchronous clock terminal in an input mode, and the synchronous clock terminal on the transmitting side. A centralized management device for a cooling storage, characterized in that a general-purpose input / output terminal is connected thereto, and a synchronous clock signal is output from the general-purpose input / output terminal to execute data transmission / reception.