JP2007057446A - Device and method for measuring pulse signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure width and period of pulse signal using a timer for generating an interrupt signal in regard to both of a pulse signal input and overflow. <P>SOLUTION: The interrupt signal is output while reloading to a reload register is performed, the interrupt signal is output without reloading to the reload register when the count value overflows, and the interrupt signal is received and the count value of the reload register is read when the pulse width or period are measured using a timer for putting an overflow flag into the ON state (step ST1). The state of the overflow flag of the timer is determined (step ST2). When the overflow flag lies in the ON state, the existence of input of the pulse signal is determined based on the comparison of the present value read from the reload register with the last value (step ST6). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pulse signal measuring apparatus and method for measuring a pulse width and a pulse period using a timer having a counter circuit.

As a timer for detecting the period and width of the pulse signal, the counter circuit counts in synchronization with the rise or fall of the pulse signal (the edge of the pulse signal) and interrupts every time the pulse signal edge is detected A device that outputs a signal is known (for example, see Patent Document 1). Therefore, the pulse width and the pulse period can be detected by reading the count value of the counter circuit in response to the generation of the interrupt request.
Japanese Patent Laid-Open No. 05-150858

By the way, in the timer, when a pulse signal having a long pulse width or cycle is input and an overflow occurs in the counter circuit, the overflow flag is turned on and the interrupt signal is turned on. In other words, the timer generates the same interrupt signal when the pulse signal is input and when an overflow occurs. Normally, in order to determine whether the interrupt signal is due to the input of a pulse signal or due to an overflow, it can be determined based on whether the overflow flag is on.
However, if a pulse signal is input with the overflow flag turned on, the interrupt request may be caused by an overflow, or an interrupt signal due to the input of the pulse signal cannot be obtained, resulting in an overflow. It was difficult to accurately measure the width and period of the pulse signal.

  The present invention has been made in view of the above circumstances, and its object is to use a timer that generates an interrupt signal for both the input of the pulse signal and the overflow of the counter circuit, An object of the present invention is to provide a pulse signal measuring apparatus and method capable of accurately measuring the period.

The pulse signal measurement method according to the present invention executes a count operation based on detection of an edge of a pulse signal, reloads the count value to the reload register, outputs an interrupt signal, and reloads when the count value overflows. A pulse signal measurement method using a timer that outputs an interrupt signal without reloading to a register and sets an overflow flag to an on state, wherein a reading step of reading a count value of a reload register in response to an interrupt signal from the timer; A flag determination step for determining the state of the overflow flag of the timer in response to an interrupt signal from the timer, and a comparison between the current count value read from the reload register and the count value when the overflow flag is on. Based on overflow hula There has been characterized as having a an input determination step of determining whether the input of the pulse signal in while on.
According to this configuration, when a new pulse signal is input (a new edge of the pulse signal is detected) while the overflow flag is on due to overflow, a new count value is reloaded into the reload register. Therefore, the presence or absence of a new pulse signal input can be detected from the value of the reload register.

In the above configuration, the input determining step determines that there is an interrupt request due to the input of a pulse signal when the count value of the current time read from the reload register and the previous time does not match, and the current time read from the reload register is the previous time When the count values match, a configuration can be adopted in which it is determined that there is no interrupt request due to input of a pulse signal.
According to this configuration, by comparing the previous value and the current value of the reload register, it is possible to detect whether a new pulse signal is input, and it is possible to detect the input of a new pulse signal while the overflow flag is on. .

In the above configuration, the pulse width or cycle of the pulse signal is calculated when it is determined that the overflow flag is off in the flag determination step, and when it is determined that there is an interrupt request due to the input of the pulse signal in the input determination step. It is possible to employ a configuration that further includes a calculation step.
According to this configuration, since an interrupt request due to overflow and an interrupt request due to input of a pulse signal are reliably distinguished, the pulse width or cycle of the pulse signal can be accurately calculated.

In the above configuration, it is possible to adopt a configuration further including a step of notifying the determination result in the input determining step.
According to this configuration, it is possible to notify an application using the count value of the timer whether an interrupt request is due to overflow or an interrupt request is due to input of a pulse signal.

In the above configuration, it is possible to employ a configuration that further includes a step of performing processing for turning off the overflow flag after notification of the determination result.
According to this configuration, since the process of forcibly turning off the overflow flag from the outside of the timer is performed, the number of occurrences of overflow can be acquired by counting the number of times the overflow flag is turned on in one count operation.

In the above configuration, it is possible to adopt a configuration further including an update step of updating the number of overflows that occurred during one count operation when it is determined that an overflow has occurred in the flag determination step.
According to this configuration, the number of overflows that occurred during one counting operation can be obtained, so that measurement is possible even when the width and period of the pulse signal are long.

In the above configuration, it is determined whether or not the number of overflows exceeds a predetermined maximum value before executing the update step, and further includes a maximum value guard processing step that does not cause the update step to be executed if it exceeds. Can be adopted.
According to this configuration, it is possible to prevent an erroneous width or cycle from being calculated.

In the above configuration, it is possible to employ a configuration that further includes a calculation step of calculating a pulse width or a cycle based on the number of overflows and the count value read from the reload register.
According to this configuration, it is possible to accurately measure a pulse signal having a long pulse width or period that causes overflow.

  The pulse signal measuring apparatus according to the present invention executes a count operation based on detection of an edge of a pulse signal, reloads the count value to the reload register, outputs an interrupt signal, and reloads when the count value overflows A pulse signal measuring device using a timer that outputs an interrupt signal without reloading to a register, receiving means for receiving an interrupt signal from the timer and reading a count value of the reload register, and receiving an interrupt signal from the timer The flag determination means for determining the state of the overflow flag of the timer, and when the overflow flag is ON, the overflow flag is ON based on the comparison with the count value of the current count value read from the reload register The presence or absence of pulse signal input between Is characterized by having an input determination unit that, the.

  According to the present invention, it is possible to accurately measure the width and period of a pulse signal having a long width and cycle by using a timer that generates an interrupt signal for both detection of an edge of the input pulse signal and overflow of the counter circuit. Become.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the accompanying drawings.
FIG. 1 is a circuit configuration diagram of a timer used in a pulse signal measuring apparatus according to an embodiment of the present invention.
As shown in FIG. 1, the timer 10 includes a pulse edge detection circuit 30, a counter reset circuit 40, an overflow flag (register) 50, a clock generation circuit 60, a counter circuit 70, a reload register 80, and the like. In the present embodiment, the timer 10 is configured as an independent circuit, but may be configured as a partial circuit of the processor.

  The pulse edge detection circuit 30 detects the edge of the pulse signal PS input from the input port 20 and outputs a pulse to the counter reset circuit 40 in response to the detection. Further, the pulse edge detection circuit 30 detects the rising edge and / or the falling edge of the pulse signal PS in accordance with each set detection mode. For example, in the mode for detecting the period of the pulse signal PS, the rising edge or the falling edge of the pulse signal PS is detected. When the pulse width of the pulse signal PS is detected, both the rising edge and the falling edge are detected. To do.

  The counter reset circuit 40 outputs a reset pulse to the counter circuit 70 in synchronization with detection of the edge of the pulse signal PS. The counter circuit 70 ends one count operation by the input of a reset pulse and starts a new count operation.

  The overflow flag 50 is turned on when the count value CT overflows in the counter circuit 70, and is a flag (register) for indicating the occurrence of overflow. When the overflow flag 50 is turned on, it remains on until it is turned off by software processing from the outside (for example, the pulse signal measuring device 100).

  The clock generation circuit 60 supplies a clock signal having a set frequency to the counter circuit 70.

The counter circuit 70 performs a counting operation based on the clock signal supplied from the clock generation circuit 60 and the reset pulse input from the counter reset circuit.
Specifically, the counter circuit 70 starts counting up when a reset pulse is input, and when the reset pulse is input next, the counter circuit 70 reloads the count value CT at that time to the reload register 80 and outputs an interrupt signal INT. The signal is output to the pulse signal measuring apparatus 100, and the up-count is started again.
When an overflow occurs during the counting operation, the counter circuit 70 outputs the interrupt signal INT without reloading the count value CT to the reload register 80, turns on the overflow flag 50, and counts up. Continue. For example, when the counter circuit 70 has a 16-bit register, overflow occurs when the count value exceeds 65536. The interrupt signal INT is output until the overflow flag 50 is turned off.

  The reload register 80 holds the count value CT determined by the counter circuit 70 until the next count value CT is determined. That is, the reload register 80 holds the previous count value CT until a new count value CT is reloaded from the counter circuit 70.

  The pulse signal measuring device 100 is constituted by, for example, hardware such as a processor and a memory, and necessary software, and executes processing to be described later.

Next, an example of processing by the pulse signal measuring apparatus 100 using the timer 10 will be described with reference to FIGS.
Here, FIG. 2 is a flowchart showing an example of processing in the pulse signal measuring apparatus, FIG. 3 is a flowchart showing an example of interrupt processing by input of a pulse signal and interrupt processing by overflow, and FIG. FIG. 5 is a timing chart showing another example of various variables.

First, before describing the processing by the pulse signal measuring apparatus 100, the operation of the timer 10 will be described with reference to FIGS. 4 and 5 are timing charts for measuring the period of the pulse signal PS.
As shown in FIG. 4B, the counter circuit 70 performs an up-counting operation in synchronization with the rising edge of the pulse signal PS (FIG. 4A), and as shown in FIG. The value of 80 is updated.
In addition, as shown in FIG. 4B, the counter circuit 70 does not update the value of the reload register 80 when the count value CT overflows, as shown in FIG. Turn on 50. This overflow flag 50 remains on until it is turned off by software.
Further, as shown in FIG. 4E, the counter circuit 70 outputs the interrupt signal INT in synchronization with the rising edge of the pulse signal PS, and outputs the interrupt signal INT in synchronization with the occurrence of the overflow. In such a case, the cause of the interrupt signal INT can be specified by detecting the state of the overflow flag 50.

  On the other hand, as shown in FIGS. 5A to 5E, when the rising edge of the pulse signal PS is input to the counter circuit pulse 70 in a state where the count value CT overflows and the overflow flag is turned on, that is, When the overflow and the input of the edge of the pulse signal PS overlap, the counter circuit 70 has already output the interrupt signal INT due to the occurrence of the overflow, so the interrupt signal INT synchronized with the rising edge of the pulse signal PS is output. Not. That is, even if the rising edge of the pulse signal PS is input to the timer 10, the interrupt signal INT synchronized with this is not obtained.

Next, processing performed by the pulse signal measuring apparatus 100 will be described with reference to FIGS.
When receiving the interrupt signal INT from the timer 10, the pulse signal measuring apparatus 100 executes a timer interrupt process shown in FIG.
In this timer interrupt process, first, the value of the reload register 80 is read and stored as the current value (step ST1).
Next, it is determined whether the overflow flag 50 is on (step ST2). If the overflow flag 50 is off, it is determined that the interrupt request from the timer 10 is due to the input of the rising edge of the pulse signal PS. Then, an interrupt process is performed by inputting a pulse signal described later (step ST3).

On the other hand, if the overflow flag 50 is on in step ST2,
A maximum value guard process is performed to determine whether the number of overflows exceeds a predetermined maximum number (for example, specified by the number of bits in the register) (step ST4). Count up (step ST5). The number of overflows is a variable in the pulse signal measuring apparatus 100, and changes every time an overflow occurs, as shown in FIGS. 4 (G) and 5 (G). The initial value of the number of overflows is zero.

Next, it is compared whether the current count value read from the reload register 80 is different from the previous count value (step ST6).
If the current count value matches the previous count value, it is determined that there is no interrupt request due to the input of the pulse signal PS, and an interrupt process due to overflow described later is executed (step ST8). .
On the other hand, if the current count value is different from the previous count value, it is determined that the pulse signal PS has been input while the overflow flag 50 is on, and a pulse signal input to be described later is input. Is executed (step ST7).

  Here, as shown in FIG. 3A, interrupt processing by inputting a pulse signal in steps ST3 and ST7, first, the pulse width or period is calculated (step ST21). The pulse width or cycle is obtained by adding the current value of the reload register 80 to the value obtained by multiplying the counter maximum value +1 of the reload register 80 by the number of overflows. Therefore, in the pulse signal measuring apparatus 100, as shown in FIG. 4 (F) and FIG. 5 (F), the pulse period (or pulse width) is calculated every time an interrupt due to the input of the pulse signal occurs.

  Next, the number of overflows is initialized (step ST22), and a process for notifying an application or the like that an interrupt request has been generated by inputting a pulse signal is performed (step ST23). As a result, the application can identify the cause of the generation of the interrupt signal INT.

  As shown in FIG. 3B, the interrupt processing due to overflow in step ST8 is processing for notifying an application or the like that an interrupt request due to overflow has occurred (step ST31). As a result, the application can reliably identify that the pulse signal has not been input while the overflow flag is on.

After completing the process of step ST7, the pulse signal measuring apparatus 100 waits for a predetermined time to elapse until the interrupt process of steps ST3, ST7, ST8 is completed (step ST9), and then the overflow flag of the timer 10 is set. As shown in FIG. 4D and FIG. 5D, a process of turning off 50 is executed (step ST10). As a result, the output of the interrupt signal INT from the timer 10 is stopped.
Next, the current value read from the reload register 80 is updated as the previous value (step ST11), and the interrupt process ends.

  As described above, according to the present embodiment, even when the overflow flag is on, it is possible to detect whether or not a pulse signal is input, so that interrupt processing synchronized with the input of the pulse signal can be reliably executed, and overflow It is possible to accurately measure a pulse signal having a long period or a width such that the above occurs.

  In the above embodiment, the case where the timer 10 and the pulse signal measuring device 100 are separately configured has been described. However, the present invention is not limited to this, and it is also possible to configure them with a single processor.

It is a circuit block diagram of the timer used for the pulse signal measuring device concerning one embodiment of the present invention. It is a flowchart which shows an example of the process in a pulse signal measuring device. (A) is a flowchart showing an example of interrupt processing by input of a pulse signal, and (B) is a flowchart showing an example of interrupt processing by overflow. It is a timing chart which shows an example of the relationship of the various variable values regarding the measurement of a pulse signal. It is a timing chart which shows the other example of the relationship of the various variable values regarding the measurement of a pulse signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Timer 20 ... Input port 30 ... Pulse edge detection circuit 40 ... Counter reset circuit 50 ... Overflow flag 60 ... Clock generation circuit 70 ... Counter circuit 80 ... Reload register 100 ... Pulse signal measuring device PS ... Pulse signal CT ... Count value

Claims (9)

Based on the detection of the edge of the pulse signal, the count operation is performed and the count value is reloaded into the reload register and an interrupt signal is output. When the count value overflows, the interrupt is performed without reloading into the reload register. A pulse signal measuring method using a timer that outputs a signal and turns on an overflow flag,
A reading step of receiving the interrupt signal from the timer and reading the count value of the reload register;
A flag determination step of determining an overflow flag state of the timer in response to an interrupt signal from the timer;
Whether or not the pulse signal is input while the overflow flag is on based on a comparison between the current count value read from the reload register and the previous count value when the overflow flag is on. An input determining step for determining;
A pulse signal measurement method comprising: The input determining step determines that there is an interrupt request due to the input of the pulse signal when the count value of the current time read from the reload register does not match the previous count value,
If the current and previous count values read from the reload register match, it is determined that there is no interrupt request due to the input of the pulse signal.
The pulse signal measuring method according to claim 1. When it is determined that the overflow flag is off in the flag determination step, and when it is determined that there is an interrupt request due to the input of the pulse signal in the input determination step, the pulse width or period of the pulse signal is calculated. A calculation step of:
The pulse signal measuring method according to claim 2. A step of notifying the determination result in the input determination step;
The pulse signal measuring method according to claim 2 or 3, characterized in that. A step of turning off the overflow flag after notification of the determination result;
The pulse signal measuring method according to claim 4. An update step of updating the number of overflows that occurred during one counting operation when it is determined that an overflow has occurred in the flag determination step;
The pulse signal measuring method according to claim 5. Before executing the update step, it is determined whether or not the number of overflows exceeds a predetermined maximum value, and if it exceeds, a maximum value guard processing step that does not cause the update step to be performed is further included.
The pulse signal measuring method according to claim 6. 8. The pulse signal measuring method according to claim 6, further comprising a calculating step of calculating the pulse width or period based on the number of overflows and the count value read from the reload register. Based on the detection of the edge of the pulse signal, the count operation is performed and the count value is reloaded into the reload register and the interrupt signal is output. When the count value overflows, the interrupt is performed without reloading into the reload register. A pulse signal measuring device using a timer for outputting a signal,
Read means for receiving the interrupt signal from the timer and reading the count value of the reload register;
Flag determining means for receiving an interrupt signal from the timer and determining the state of an overflow flag of the timer;
Whether or not the pulse signal is input while the overflow flag is on based on a comparison between the current count value read from the reload register and the count value when the overflow flag is on. An input discriminating means for judging;
A pulse signal measuring device comprising:

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