JP2012165048A - Time stamp acquisition device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire a time stamp of minute time without incorporating high-definition hardware.SOLUTION: A time stamp acquisition device (107) includes: a first clock time update process part (108, 108a) for obtaining timer information T when grasping an event of carrying of the minimum digit of the timer information of a timer circuit; a second clock time update process part (108, 108b) for calculating, when resetting the count value of a watch-dog timer, a cumulative count value C since obtaining a pre-reset count value and grasping the event of carrying of the minimum digit of the timer information; and a time stamp generation process part (109) for calculating, when a predetermined event occurs, a cumulative count value (C+Cm) since obtaining a count value Cm of the watch-dog timer and grasping the event of carrying of the minimum digit of the timer information and calculating a time stamp value Ts from the cumulative count value (C+Cm), time Δt required for one-count and the timer information T.

Description

  Embodiments described herein relate generally to a time stamp acquisition apparatus and a time stamp acquisition method using a watch dog timer.

  Information processing apparatuses often require a function of acquiring time information (time stamp) when a predetermined event occurs. With the recent increase in information processing speed, the minimum unit of time information to be acquired has become finer. For example, acquisition of time information in the microsecond order is required. When acquiring such minute time information, a method using a dedicated internal clock provided inside the information processing apparatus is known (for example, see Patent Document 1).

JP 2009-49554 A

  However, in order to acquire fine time information, a high-definition internal clock is required, leading to an increase in hardware costs. Also, depending on the information processing apparatus, it may be difficult to mount a high-definition internal clock due to hardware restrictions.

  Therefore, there is a need for a technique that can acquire a time stamp of fine time without installing special hardware.

  According to the embodiment of the present invention for solving the above-described problem, the first time update process for acquiring the time information T when it is grasped that the minimum digit of the time information of the time circuit has generated a carry. And when the count value of the watchdog timer is reset, the count value before the reset is obtained and the accumulated count value C is calculated after grasping that the minimum digit of the timekeeping information has been raised. 2 and the cumulative count value (C + Cm) after acquiring the count value Cm of the watchdog timer and grasping that the minimum digit of the timekeeping information has been raised when a predetermined event occurs. A time stamp including a cumulative count value (C + Cm), a time Δt required for one count, and a time stamp generation processing unit for calculating a time stamp value Ts from the timekeeping information T The resulting device is provided.

The block diagram for demonstrating the structural example of the information processing apparatus carrying the time stamp acquisition apparatus which concerns on this embodiment. The figure for demonstrating operation | movement of the watchdog timer of embodiment. The figure which shows the operation | movement procedure of the time update process part of this Embodiment. The figure which shows the operation | movement procedure of the time stamp production | generation process part of this Embodiment. The figure which shows the operation | movement procedure of the time update process part of 2nd Embodiment. The figure which shows the operation | movement procedure of the time update process part of 2nd Embodiment.

[First Embodiment]
Hereinafter, a time stamp acquisition apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram for explaining a configuration example of an information processing apparatus equipped with a time stamp acquisition apparatus according to this embodiment.
As illustrated in FIG. 1, the information processing apparatus 100 includes a CPU 101, an RTC (real time clock) 102, a WDT (watchdog timer) 103, a program memory unit 104, and a memory unit 105.

  The CPU 101 sequentially executes instructions incorporated in the information processing apparatus 100 in synchronization with the clock signal. The RTC 102 is a clock circuit that generates real time (year / month / day / hour / minute / second). The WDT 103 counts the clock signal, and outputs a CPU interrupt indicating the occurrence of an abnormality to the CPU 101 when the count value exceeds a predetermined value. Note that the CPU 101, the RTC 102, and the WDT 103 are configured on the same CPU board.

  The program memory unit 104 stores a program for controlling the information processing apparatus 100. The memory unit 105 stores various data. The memory unit 105 may be composed of a volatile memory, for example, a nonvolatile memory such as an EEPROM or a flash ROM that can write and rewrite data.

  The program memory unit 104 includes an application unit 106 and a time stamp acquisition unit 107. The time stamp acquisition unit 107 is provided with a time update processing unit 108 and a time stamp generation processing unit 109. The application unit 106 is an application program that controls the information processing apparatus 100. The time stamp acquisition unit 107 executes time stamp acquisition. The time update processing unit 108 and the time stamp generation processing unit 109 will be described in detail later.

  FIG. 2 is a diagram for explaining the operation of the watchdog timer according to the embodiment. The horizontal axis in FIG. 2 represents the elapsed time, and the vertical axis represents the count value by the WDT 103. The count value is set with an error threshold.

  After the information processing apparatus 100 is activated, the WDT 103 is cyclically activated and adds a count. The period counted by the WDT 103 is, for example, on the order of μ seconds corresponding to the clock frequency of the CPU. On the other hand, the application unit 106 is activated at a predetermined cycle and instructs the WDT 103 to reset the count value. Receiving the reset instruction, the WDT 103 resets the count value and newly starts counting from zero.

  As shown in FIG. 2, the count value is reset at the time intervals C1, C2, C3..., And thus the count value does not reach the threshold value. At this time, the time interval is set to m (millisecond) order, for example. The application unit 106 can output a reset instruction at a set time interval when the information processing apparatus 100 is operating normally. However, if the information processing apparatus 100 falls into an abnormal state where it cannot continue processing, the application unit 106 cannot output a reset instruction. As a result, the count value exceeds the threshold value, and the WDT 103 outputs an exception (abnormal state occurrence) interrupt to the CPU 101.

  In this embodiment, a fine time stamp is acquired using the WDT 103.

  FIG. 3 is a diagram illustrating an operation procedure of the time update processing unit 108 according to the present embodiment. The time update processing unit 108 is activated when the application unit 106 outputs a reset instruction.

  In step S <b> 01, the time update processing unit 108 acquires real time (RTC value) from the RTC 102. Then, the acquired RTC value is substituted into the internal variable Tn. In step S02, it is checked whether the acquired RTC value (Tn) is equal to the RTC value (T) acquired at a predetermined time in the past. Here, the minimum unit of the RTC value is 100 milliseconds to seconds. Therefore, the order is different from the count value in units of μ seconds handled by the WDT 103. For this reason, the time update processing unit 108 is activated a plurality of times until the minimum unit of the RTC value causes a carry.

  When the acquired RTC value (Tn) is not equal to the RTC value (T) acquired at a predetermined time in the past (No in S02), T is updated with the RTC value (Tn) acquired this time. That is, when the minimum unit of the RTC value has a carry, the latest RTC value is stored. Then, the accumulated count value (C) is cleared to zero.

  When the acquired RTC value (Tn) is equal to the RTC value (T) acquired at a predetermined time in the past (Yes in S02), the count value counted by the WDT 103 is acquired in step S05, and the value is substituted into the internal variable Cn. To do. The count value Cn is a value corresponding to the time intervals C1, C2, C3,. In step S06, the count value Cn is added to the cumulative count value (C). Therefore, the cumulative count value (C) is a cumulative value of the count value after grasping that the minimum unit of the RTC value has caused a carry. The RTC value (T) is an RTC value when grasping that the minimum unit of the RTC value has caused a carry.

  The accumulated count value (C) and the RTC value (T) are stored in the memory unit 105 and can be referred to as appropriate by the application unit 106.

  FIG. 4 is a diagram illustrating an operation procedure of the time stamp generation processing unit 109 according to the present embodiment. The time stamp generation processing unit 109 is activated when a request for generating a time stamp is issued. For example, when a predetermined event occurs and it is desired to acquire a time stamp at that time, the time stamp generation processing unit 109 is activated.

In step S11, the count value counted by the WDT 103 is acquired, and the value is substituted into the internal variable Cm. In step S12, the fine time correction value (t) is calculated based on the equation (1).
t = (C + Cm) / frequency (1)
Here, the frequency is the reciprocal of one count time of the WDT 103. For example, the WDT 103 may be configured to count at the CPU clock frequency, or configured to count at a frequency obtained by dividing the CPU clock frequency (for example, 1/2, 1/3,...). You may do it. Further, the fine time correction value (t) may be calculated using the time Δt required for one count.
The fine time correction value (t) obtained by the equation (1) represents an elapsed time after grasping that the minimum unit of the RTC value has caused a carry.

In step S13, the time stamp value Ts is calculated based on the equation (2).
Ts = T + t Formula (2)
According to this equation (2), the time stamp value is expressed as a value in units of μ seconds handled by the WDT 103.

[Second Embodiment]
In the second embodiment, the operation procedure of the time update processing unit is different from that of the first embodiment. Accordingly, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the first embodiment, the time update processing unit 108 is activated when the application unit 106 outputs a reset instruction. Therefore, the RTC value minimum unit does not exactly match the timing at which the carry occurs. However, the accuracy of the time stamp calculated in the first embodiment is significantly improved as the order is different from the accuracy of the time stamp according to the conventional RTC value, so that sufficient accuracy is ensured depending on the application target. is doing.

  In the second embodiment, the accuracy of the time stamp is further improved. In the second embodiment, the time update processing unit 108 includes a time update processing unit 108a and a time update processing unit 108b.

  FIG. 5 is a diagram illustrating an operation procedure of the time update processing unit 108a according to the second embodiment. The time update processing unit 108a is activated when a carry occurs in the minimum unit of the RTC value.

  In step S <b> 21, the time update processing unit 108 a acquires real time (RTC value) from the RTC 102. Then, the acquired RTC value is substituted into the internal variable Tn. In step S22, the acquired RTC value (Tn) is substituted into the RTC value (T) acquired when the last unit of the RTC value has a carry. In step S23, the accumulated count value (C) is cleared to zero. In step S24, the count value of the WDT 103 is acquired and substituted for the carry count value (Ck).

  The accumulated count value (C), the RTC value (T), and the carry count value (Ck) are stored in the memory unit 105 and can be referred to by the application unit 106 as appropriate.

  FIG. 6 is a diagram illustrating an operation procedure of the time update processing unit 108b according to the second embodiment. The time update processing unit 108b is activated when the application unit 106 is cyclically activated and outputs a reset instruction.

  In step S25, the time update processing unit 108b acquires the count value counted by the WDT 103, and substitutes the value into the internal variable Cn. The count value Cn is a value corresponding to the time intervals C1, C2, C3,. In step S26, the count value Cn is added to the accumulated count value (C), and the count value (Ck) at the time of carry is further subtracted. Therefore, the cumulative count value (C) is the cumulative value of the count value after the minimum unit of the RTC value has been raised. In step S27, the carry count value (Ck) is cleared to zero.

  The accumulated count value (C), the RTC value (T), and the carry count value (Ck) are stored in the memory unit 105 and can be referred to by the application unit 106 as appropriate.

  The operation of the time stamp processing unit according to the second embodiment is the same as the operation of the time stamp processing unit according to the first embodiment, and thus detailed description thereof is omitted.

  According to the second embodiment, it is necessary to input a carry signal of the minimum digit from the RTC 102. However, since it is not necessary to update the RTC 102 to a high-accuracy one, a high-accuracy time stamp is obtained at a low cost. be able to.

  Note that the functions described in the above-described embodiments are not limited to being configured using hardware, and can be realized by causing a computer to read a program describing each function using software. Each function may be configured by appropriately selecting either software or hardware.

Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage.
Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  DESCRIPTION OF SYMBOLS 100 ... Information processing apparatus 101 ... CPU, 102 ... RTC, 103 ... WDT, 104 ... Program memory part, 105 ... Memory part, 106 ... Application part, 107 ... Time stamp acquisition part, 108, 108a, 108b ... Time update process 109, a time stamp generation processing unit.

Claims (6)

Accumulated counts of the watchdog timer after grasping that the timekeeping information T when the minimum digit of the timekeeping information of the timekeeping circuit has generated a carry, the minimum digit of the timekeeping information having generated a carry A time stamp acquisition device that calculates a time stamp value Ts by the following equation using a value C, a count value Cm of a watchdog timer when a predetermined event occurs, and a time Δt required for one count of the watchdog timer .
Ts = T + (C + Cm) × Δt   2. The time stamp acquisition apparatus according to claim 1, wherein when the count value of the watchdog timer is reset, it is determined whether or not a carry has occurred in the minimum digit of the time information.   2. The time stamp acquisition apparatus according to claim 1, wherein the time stamp acquisition apparatus recognizes that a carry has occurred in a minimum digit of the time measurement information based on a signal from the time measurement circuit. A first time update processing unit for acquiring the time information T when the minimum digit of the time information of the time circuit grasps that a carry has occurred;
When resetting the count value of the watchdog timer, the second time for calculating the cumulative count value C after acquiring the count value before resetting and grasping that the minimum digit of the timekeeping information has been raised An update processing unit;
When a predetermined event occurs, the count value Cm of the watchdog timer is acquired, and the cumulative count value (C + Cm) is calculated after grasping that the minimum digit of the timekeeping information has generated a carry. C + Cm) A time stamp acquisition apparatus comprising: a time Δt required for one count; and a time stamp generation processing unit that calculates a time stamp value Ts from the timekeeping information T. Accumulated counts of the watchdog timer after grasping that the timekeeping information T when the minimum digit of the timekeeping information of the timekeeping circuit has generated a carry, the minimum digit of the timekeeping information having generated a carry A time stamp acquisition method, wherein a time stamp value Ts is calculated by the following equation using a value C, a count value Cm of a watchdog timer when a predetermined event occurs, and a time Δt required for one count of the watchdog timer .
Ts = T + (C + Cm) × Δt Acquire the time information T when the minimum digit of the time information of the time circuit grasps that the carry has occurred,
When resetting the count value of the watchdog timer, the cumulative count value C after obtaining the count value before resetting and grasping that the minimum digit of the timekeeping information has been generated is calculated,
When a predetermined event occurs, the count value Cm of the watchdog timer is acquired and the cumulative count value (C + Cm) is calculated after grasping that the minimum digit of the timekeeping information has been raised,
A time stamp acquisition method, wherein a time stamp value Ts is calculated from a cumulative count value (C + Cm), a time Δt required for one count, and the time information T.

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