JP3775115B2 - Standard time setting method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a standard time setting method and a setting device among a plurality of devices.
[0002]
[Prior art]
In a plurality of devices each equipped with a clock and transferring information via a common transmission line, the time of the clock of the other device is adjusted based on the standard time of the device having the clock that generates the standard time. A method of performing this method is known (for example, see Japanese Patent Application Laid-Open No. 05-158826).
[0003]
In this specification, a standard time among a plurality of devices is referred to as a standard time, a clock that generates the standard time is a standard clock, a device equipped with the standard clock is a standard time device, and a standard time is set in the built-in clock. The device is called a device to be set.
[0004]
In the above-described conventional standard time setting method, a request for providing standard time is transmitted from the set device to the standard time device, and half of the required time until the standard time is received from the standard time device is set to the provided standard time. It is corrected by adding, and the standard time after correction is set in the built-in clock.
[0005]
[Problems to be solved by the invention]
By the way, when a lot of information is transmitted and received on the transmission line and the transmission line is congested, a delay occurs in the transmission time of the standard time provision request, the transmission time of the standard time, or both.
[0006]
However, in the above-mentioned conventional standard time setting method in which half of the time required from the request for provision of standard time to reception of the standard time is used as a transmission delay time and added to the standard time, the standard time is provided because the transmission path is congested. If there is a delay between the transmission and reception of the request and the standard time, an error occurs in the transmission delay time of the correction value, and there is a problem that an accurate standard time cannot be set.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide a standard time setting method and apparatus for accurately adjusting the time to the standard time regardless of the congestion state of the transmission path.
[0008]
[Means for Solving the Problems]
The present invention will be described with reference to FIGS. 1 to 3 showing an embodiment.
(1) According to the first aspect of the present invention, serial communication of a microcomputer is performed between a plurality of devices via a common transmission line L, and the time of the first clock 3 of the first device UO is set as the standard time ts. A standard time setting method for setting the second timepiece 13 of the device UA, in which the first device UO transmits a time reading request of the second timepiece 13 to the second device UA (S1 in FIG. 3). ) And the second procedure UA reads the time Ta of the second timepiece 13 when the time reading request is received, and transmits a reception completion signal ACK to the first device UO (S2 to S4 in FIG. 3). When the first device UO receives the reception completion signal ACK, the third procedure of reading the time To of the first watch 3 and transmitting the time To to the second device UA (S14 to S15 in FIG. 3), the second device UA, first from the reception of the time read request A delay time Delta] t 1 until reading time Ta of the clock 13, from the reception of the time read request in consideration of the delay time Delta] t 2 until reading time To of the first clock 3, the time of the second clock 13 The fourth procedure (S5 to S7 in FIG. 3) for correcting ta by the time difference {(Ta−Δt 1 ) − (To−Δt 2 )} is executed, and the second watch 13 is set to the standard of the first watch 3. Time ts is set.
(2) According to the invention of claim 2, serial communication of a microcomputer is performed between a plurality of devices via a common transmission line L, and the time ts of the first clock 3 of the first device U O is set as the standard time. a setting device of a standard time to be set to the second clock 13 of the second device U a, first means 1 of the first apparatus U O for transmitting time read request to the second clock 13 to the second device U a, 2 and the second means 11 and 12 of the second device U A for reading the time Ta of the second clock 13 when receiving the time reading request and transmitting the reception completion signal ACK to the first device U O , and reception completion with reading time T o of the first clock 3 Upon receipt of the signal ACK, receives a first unit U third means 1 and 2 O for transmitting time T o to a second device U a, the time read request Delay time Δt 1 until the time Ta of the second clock 13 is read and the time reading Taking into account the delay time Δt 2 from the reception of the request to read the time To of the first clock 3 , the time difference of the second clock {(Ta−Δt 1 ) − (To−Δt 2 ) } , And the fourth means 11 and 12 of the second device U A for correcting by the second time 13, and the standard time ts of the first timepiece 3 is set in the second timepiece 13.
[0009]
In the section of the means for solving the above-described problem, a diagram of an embodiment is used for easy understanding of the description. However, the present invention is not limited to the embodiment.
[0010]
【The invention's effect】
According to the present invention, communication is performed between a first device having a first timepiece and a second device having a second timepiece, and the time of the first timepiece is set as the standard time to the second timepiece. When setting, first, the time reading request of the second clock is transmitted to the second device. When the time reading request is received, the time Ta of the second clock is read and a reception completion signal is transmitted to the first device. Next, when the reception completion signal is received, the time To of the first clock is read and the time To is transmitted to the second device. When the time To is received, the time of the second clock is corrected by the time difference (Ta-To), and the standard time of the first clock is set in the second clock, so that the transmission line is congested. However, the standard time can be accurately set in the second clock of the second device.
It should be noted that a delay time Δt1 from the reception of the time reading request to the reading of the time Ta of the second clock and a delay time Δt2 from the reception of the time reading request to the reading of the time To of the first clock are taken into consideration. Thus, by correcting the time of the second clock by the time difference {(Ta−Δt1) − (To−Δt2)}, the standard time can be set more accurately in the second clock of the second device.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing a configuration of an embodiment.
The standard clock device UO and the set devices UA, UB,... Perform serial communication via a common transmission line L. This serial communication is performed according to a predetermined communication protocol. The standard clock device UO includes a communication interface 1, a processing circuit 2, a standard clock 3, a memory 4, and the like. The processing circuit 2 has a microcomputer and performs calculation and control. The standard clock 3 generates a standard time as a reference among the devices UO, UA, UB,... That communicate via the common transmission line L. The set device UA includes a communication interface 11, a processing circuit 12, a clock 13, a memory 14, and the like. The processing circuit 12 has a microcomputer and performs calculation and control. The clock 13 is dedicated to the set device UA, and the time is set by the standard clock 3 in the standard time setting process described later, and the standard time is set. The other set devices UB,... Have the same configuration as the set device UA, and a description thereof will be omitted.
[0012]
FIG. 2 is a diagram for explaining the standard time setting principle of the embodiment. Here, the standard time setting process between the standard time device UO and the set device UA will be described as an example, but the standard time between the standard time device UO and the other set devices UB,. The setting process is the same, and the description thereof is omitted.
This standard time setting process may be performed, for example, every predetermined time, or may be performed in an initialization process immediately after starting the set target devices UA, UB,.
[0013]
The standard time generated by the standard clock 3 of the standard time device UO is denoted by ts, and the time generated by the internal clock 13 of the set device UA (hereinafter referred to as the internal time) is denoted by ta. First, the set device UA requests the standard time device UO to provide the standard time ts in order to adjust the time of the internal clock 13 to the standard time ts. The standard time device UO that has received the standard time provision request transmits an internal time reading request to the set device UA. This internal time reading request requests the set device UA to read the time of the internal clock 13, and the read internal time is used for setting the standard time.
[0014]
The set device UA that has received the “internal time reading request” communication frame transmits a reception completion signal ACK to the standard time device UO, reads the current time from the internal clock 13, and sets the time as the internal time Ta. . Note that the delay time from when the communication frame of “internal time reading request” is received to when the request content is decoded and the internal time Ta is actually read is denoted by Δt1.
[0015]
Upon receiving the internal time reading request reception completion signal ACK, the standard time unit UO immediately reads the current time from the standard clock 3 and sets the time as the standard time To. It should be noted that the delay time from when the set device UA receives the communication frame of “internal time reading request” until the reception completion signal ACK is returned to the standard time device UO and the standard time device UO actually reads the standard time To. Is Δt2. The standard time device UO sends the read standard time To to the set device UA.
[0016]
Here, a delay time Δt1 until the set device UA reads the internal time Ta from the time when the set device UA receives the internal time reading request ((1) in FIG. 2) and the standard time device UO Consider the delay time Δt2 until the standard time To is read.
The delay time Δt1 from when the internal time reading request is received until the request content is decoded and the internal time Ta is actually read is determined by the processing speed of the microcomputer and is usually extremely short.
[0017]
In general, microcomputer serial communication between devices is performed according to a communication protocol that returns a reception completion signal ACK frame as soon as a communication frame is received from another device, from reception completion to completion signal ACK return. The time delay is extremely short. Further, the time from when the standard time unit UO receives the reception completion signal ACK until the standard time To is actually read is determined by the processing speed of the microcomputer and is usually extremely short. Accordingly, the delay time Δt2 from when the set device UA receives the internal time reading request until the standard time device UO reads the standard time To is also extremely short.
[0018]
Further, as shown in FIG. 2, both the delay time Δt1 until the set device UA reads the internal time Ta and the delay time Δt2 until the standard time device UO reads the standard time To are both set by the set device UA. This is a time delay starting from the time point (1) when the internal time reading request is received from the standard time unit UO. In the standard time setting process, these delay times Δt1 and Δt2 are offset from each other, resulting in a standard time setting error. Will be reduced.
[0019]
Therefore, in this embodiment, both the delay times Δt1 and Δt2 are set to 0, the internal time reading request is received by the set device UA and the internal time Ta is read, and the reception completion signal ACK is received by the standard time device UO. It is the same time as when the standard time To was received and read.
[0020]
If the internal clock 13 of the set device UA and the standard clock 3 of the standard time device UO generate the same time, the internal time Ta read at the same time and the standard time To should match. If the internal time Ta read at the same time and the standard time To are different, the time difference (Ta-To) between them is the time between the internal clock 13 of the set device UA and the standard clock 3 of the standard time device UO. It is a gap. Therefore, in the set device UA, the current time ta is corrected by the time difference (Ta−To) by the following equation to obtain a new time ta ′.
[Expression 1]
ta ′ = ta− (Ta−To)
[0021]
As a result, the standard time ts of the standard time device UO is set in the internal clock 13 of the set device UA, and the internal clock 13 of the set device UA generates the same time as the standard clock 3 of the standard time device UO.
[0022]
FIG. 3 is a flowchart showing a standard time setting process executed by the processing circuit 12 of the set device UA and the processing circuit 2 of the standard time device UO. The operation of the embodiment will be described with reference to these flowcharts.
In step 1, the set device UA transmits a standard time provision request to the standard time device UO. The standard time device UO confirms the reception of the standard time provision request in step 11, and if the standard time provision request is received from the set device UA, the standard time device UO proceeds to step 12 and transmits an internal time reading request to the set device UA. In step 13, the transmission completion of the internal time reading request is monitored.
[0023]
The set device UA confirms the reception of the internal time reading request in step 2, and if it receives the internal time reading request from the standard time device UO, it proceeds to step 3 and transmits a reception completion signal ACK to the standard time device UO. In step 4, the current time is read from the internal clock 13 and stored in the memory 14 as the internal time Ta.
[0024]
The standard time unit UO confirms whether or not the transmission of the internal time reading request has been completed in step 14, that is, whether or not the reception completion signal ACK of the set device UA indicating the completion of transmission has been received, and receives the reception completion signal ACK. Then, the process proceeds to step 15 where the current time is read from the standard clock 3 and transmitted to the set device UA as the standard time To.
[0025]
The set device UA confirms the reception of the standard time To in step 5 and calculates the time difference (Ta−To) from the internal time Ta stored in the memory 13 when the standard time To is received from the standard time device UO. To do. In the following step 7, the time difference (Ta−To) is substituted into the above equation 1 to correct the time ta of the internal clock 13 to obtain a new time ta ′.
[0026]
In this way, communication is performed between the standard time device UO having the standard clock 3 and the set device UA having the internal clock 13 via the transmission line L, and the time of the standard clock 3 is set as the standard time ts. When setting the internal clock 13 of the setting device UA, a time reading request of the internal clock 13 is transmitted from the standard time device UO to the set device UA, and when the time reading request is received by the set device UA, the time of the internal clock 13 is set. While reading Ta, a reception completion signal is transmitted to the standard time unit UO. Next, when the reception completion signal is received by the standard time device UO, the standard time To of the standard clock is read and the standard time To is transmitted to the set device UA. When the set device UA receives the standard time To, the time ta of the internal clock 13 is corrected by the time difference (Ta-To), and the standard time ts of the standard clock 3 is set in the internal clock 13. Even when the transmission line is congested, the standard time ts can be accurately set in the internal clock 13 of the set device UA.
[0027]
In the embodiment described above in the base point when the target setting unit UA receives the internal time read request, the delay time Δt1 until reading the internal time Ta, the standard time unit UO reads the standard time To Both the delay time Δt2 and the delay time Δt2 are set to 0. However, when the standard time setting process is performed in consideration of these delay times Δt1 and Δt2, the new time ta ′ may be obtained by the following equation instead of Equation 1. . As described above, the delay times Δt1 and Δt2 are substantially determined by the processing capability of the microcomputer and are always constant, so that they are measured and stored in advance.
[Expression 2]
ta ′ = ta − {(Ta−Δt1) − (To−Δt2)}
When only the delay time Δt1 is considered and the delay time Δt2 is set to 0, the new time ta ′ is obtained by the following equation instead of the equation 1.
[Equation 3]
ta ′ = ta − {(Ta−Δt1) −To}
Further, when only the delay time Δt2 is considered and the delay time Δt1 is set to 0, the new time ta ′ is obtained by the following equation instead of the equation 1.
[Expression 4]
ta ′ = ta− {Ta− (To−Δt 2)}
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an embodiment.
FIG. 2 is a diagram for explaining the principle of setting a standard time according to one embodiment.
FIG. 3 is a flowchart illustrating a standard time setting operation according to an embodiment.
[Explanation of symbols]
UO Standard clock device UA, UB Device to be set 1, 11 Interface 2, 12 Processing circuit 3 Standard clock 4, 14 Memory 13 Clock

Claims (2)

A standard time setting method in which serial communication of a microcomputer is performed between a plurality of devices via a common transmission line, and the time of the first clock of the first device is set as the standard time to the second clock of the second device. There,
A first procedure for transmitting a time reading request of the second clock to the second device by the first device;
When the second device receives a time reading request, the second procedure reads the time Ta of the second clock and transmits a reception completion signal ACK to the first device;
When the first device receives the reception completion signal ACK, the third procedure reads the time To of the first clock and transmits the time To to the second device;
Delay time Δt 1 from receiving the time reading request to reading the time Ta of the second clock by the second device, and delay time Δt from receiving the time reading request to reading the time To of the first clock 2 and the fourth procedure for correcting the time of the second clock by the time difference {(Ta−Δt 1 ) − (To−Δt 2 )} . A standard time setting method characterized by setting a standard time. A standard time setting device that performs serial communication of a microcomputer via a common transmission line between a plurality of devices and sets the time of the first clock of the first device as the standard time to the second clock of the second device. There,
A first means of the first device for transmitting a time reading request of the second clock to the second device;
A second means of the second device for reading the time Ta of the second clock when receiving the time reading request and transmitting a reception completion signal ACK to the first device;
A third means of the first device for reading the time T o of the first clock upon receiving the reception completion signal ACK and transmitting the time T o to the second device;
Time and the delay time Delta] t 1 from the reception of the read request until it reads the time Ta of the second clock, in consideration of the delay time Delta] t 2 from the reception of the time read request to read the time To of the first clock And a fourth means of the second device for correcting the time of the second clock by the time difference {(Ta−Δt 1 ) − (To−Δt 2 )}, and the second clock has a standard time of the first clock. A standard time setting device, characterized in that

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