KR940009815B1 - Frequency detecting apparatus and method using directport of microcomputer - Google Patents

Abstract

The device consists of a micom (1) for giving sampling pulses or sampling intervals through serial ports and measuring the frequency of a high and a low input signals (Fh,Fl), a timing processing part (4) for operating frequencys of input signals (Fh,Fl) by control of the micom, a counter (5) for counting frequency of input signals (Fh,Fl) by control of the micom, and a parallel/serial latch (7) for transferring outputs of the counter into the micom (1) in parallel or serial.

Description

Frequency measuring device and method using serial port of microcomputer

1 is a block diagram of a frequency measuring device of the present invention.

Figure 2 (a) to (h) is a signal timing diagram for explaining the operation of the apparatus of the present invention.

3 is an interrupt flowchart for explaining the method of the present invention.

4 is a timer interrupt flowchart for explaining the method of the present invention.

5 is a block diagram of a conventional frequency measuring apparatus of Embodiment 1.

6 is a block diagram of a second embodiment of a conventional frequency measuring device.

7 (a) to (d) are signal timing diagrams of the first embodiment.

8 (a) to (d) are signal timing diagrams of the second embodiment.

9 is a graph showing the error rate of the conventional Example 1 and Example 2.

* Explanation of symbols for main parts of the drawings

1: Micom 2, 3: NAND Gate

4: timing processing unit 5: counter

6: parallel / serial latch 1: counter / latch

The present invention relates to a frequency measuring apparatus and method using the serial port of the microcomputer, in particular, to provide a sampling pulse or a sampling time by using the serial port of the microcomputer to count the frequency over the broadband. Conventional frequency measuring apparatus can be divided into two cases as shown in FIG. 5 and FIG.

First, the operation of the frequency measuring apparatus shown in FIG. 5 according to the first embodiment of the conventional apparatus will be described with reference to FIGS. 7A through 7D, and the output of the reference clock generator 101 is As the signal to be supplied to the clock and to measure the frequency is input to the timing generator 103 through the input terminal IN, the timing generator 103 is outputted so that the clear signal CLEAR of the counter 102 and the latch of the arrangement 104 can be obtained. The signals LATCH are respectively output.

After the latch signal is supplied to the latch 104 and the output value of the counter 102 is latched, when the clear signal is supplied to the counter 102 and the counter 102 is cleared, the latched value is transmitted through the output terminal OUT. Supplied to the processor. The processor converts the frequency based on the frequency measurement data. In this case, if the reference clock frequency is fs and the input signal is fi, the Gaussian symbol is used to write fs ÷ fi⇒ [ fs / fi] = N and the data for fi becomes a counter value of N or N-1 and the resolution becomes larger as fs increases the operation of the frequency measuring apparatus shown in FIG. Referring to (a) to (d) of FIG. 8, an input signal for measuring a frequency during the sampling period Ts of the reference clock output from the reference clock generator 105 is inputted through the counter gate 107. The timing generator 108 supplies a latch signal to the latch 109 to latch the count value, and then supplies a clear signal to the counter 107 to clear the counter 107 and reset the latched value. Frequency measurement data The processor performs the operation for converting the frequency.

In this case, if the frequency of the input signal is fi ', the Gaussian signal: [] is used to write Ts / fi' ^(-1) = Ts × fi'⇒ [Ts] = N and the data for fi 'is N. Alternatively, the counter value becomes N-1, and the resolution becomes larger as Ts increases. The relationship between the error rates with respect to the frequencies of the first and second embodiments is as shown in FIG. 9, in the case of the first embodiment, a good error rate is shown in the low frequency band, and in the second embodiment, the error rate is good in the high frequency band. It can be called a counter or a high frequency counter.

However, such a conventional apparatus requires a processor to delay the execution of an instruction cycle, so that the high frequency processing is not suitable programmatically, and thus the processor is limited to the purpose of receiving and displaying only frequency measurement data. There is a problem that the configuration becomes complicated due to a large burden, and when the processor is responsible for hardware timing and reference clock generation, the delay time (see FIGS. 7b, c and 8c, d) is increased and the error rate is increased, thereby increasing frequency accuracy. And there was a problem that the reliability is lowered.

In addition, in this case, the program execution of the processor itself is performed in parallel with the timing and clock generation, and the error rate is randomly generated according to the size of the previous instruction cycle. In order to solve the conventional problems, the present invention greatly simplifies the hardware of the frequency measuring device by using a serial port that is divided into a reference microcomputer, and enhances the software function to stabilize the accuracy when employing a high speed command cycle microcomputer. It is an object of the present invention to provide a frequency measuring apparatus and method using a serial port of the microcomputer that can ensure a reliable frequency measurement over a wide band, the present invention will be described in detail by the accompanying drawings as follows. .

The frequency measuring device of the present invention, as shown in FIG. 1, provides a sampling pulse or a sampling period through the serial port to measure the frequency of the high and low frequency input signals Fh and Fl, and the microcomputer 1 1) a timing processor 4 comprising NAND gates 2 and 3 for performing the gate operation of the input signals (Fh, Fl) under the control of 1), and an input signal Fh, under the control of the microcomputer 1; A counter / latch portion 7 comprising a counter 5 for counting the frequency of Fl and a command / serial latch 6 for transmitting the output value of the counter 5 to the timing 1 in parallel-serial; It is composed.

The operation and effect of the apparatus of the present invention configured as described above is a high frequency input signal Fh and a low frequency input with respect to the input signals Fh and Fl to measure the frequency as shown in FIGS. 1 and 2 (a) to (h). The count of the signal Fl is performed simultaneously. First, the frequency measurement of the low frequency input signal Fl will be described. The input signal Fl is an interrupt terminal of the microcomputer 1. In this case, the frequency measurement is performed as described above. In this case, as shown in FIG.

In the section where CA = 0, the low-frequency selection signal LSEL of the microcomputer 1 becomes high according to the down edge trigger of the input signal Fl, and the low-frequency selection signal LSEL of the microcomputer 1 goes low at the next down edge. do. (See also section 2e.)

Serial sampling clock output from microcomputer 1 during low frequency selection signal LSEL This NAND gate is input to the counter 5 through the NAND gate 2 and counted, and the count value is a serial sampling clock which passes for one period of the input signal Fl. It becomes a number.

At this time, the frequency of the input signal Fl is Fl and the serial sampling clock If the frequency of fs (= sampling frequency) is [fs ÷ fl] = N, the count number is N or N-1.

In this case, however, the following conditions must be preceded.

That is, the instruction execution time (Tm) of the time when the low frequency selection signal LSEL becomes active high and the time low when interrupting through the microcomputer 1 should be less than 1 / fs, and if Tm <1 / fs, the low frequency count The error occurrence is reduced in time, which means that the number of counts is N or N-1.

Implementing Tm <1 / fs like this requires that the count must be in units of 0.5 Hz in order to count at 1 Hz with precision up to fl = 100 Hz. ] 2 is possible, and fs / 99.5-fs / 100≥2 yields Tm <25.1μsec since fs≥39.8KHz and 1 / fs = 25.1μsec.

The reason for this is that since the Tm of the microcomputer 1 generally reaches several hundred nsec to several microseconds, the Tm has a value sufficiently smaller than 25.1 microseconds so that it does not affect the number of counts. For low frequencies, set the correct sampling frequency (fs) You can output In the case of the low frequency count, the lower the fl and the larger the fs, the greater the precision.

On the other hand, in the case of frequency measurement on the input signal Fh of the high frequency, the microcomputer 1 outputs the high frequency selection signal HSEL for the sampling time Ts as shown in FIG. 2C, and the NAND gate 3 during this time. The frequency measurement is performed by counting the frequency of the input signal Fh input to the counter 5 through). In this case, as shown in FIG. When the high frequency selection signal HSEL becomes high during the sampling time Ts in the section where CA = 1, the count counted by the counter 5 during this period is parallel / loaded by the load signal LD supplied from the microcomputer 1. The data of the parallel / serial latch 6 is input to the data input terminal IN of the microcomputer 1 by being loaded into the serial latch 6 (see also FIG. 2F), and as shown in FIG. 2G, by the clock CK. The frequency fh of the input signal Fh is measured and a clear signal is supplied from the microcomputer 1 to the counter 5 as shown in FIG. 2h to clear the counter 5 to prepare for the next operation. Initialization) Even when measuring the frequency of the high frequency input signal Fh, the accurate sampling time Ts can be output by using the serial port of the microcomputer 1, thereby making it possible to accurately measure the high frequency frequency fh.

The accurate sampling time Ts can be output in this manner as shown in FIG. 2D. The serial sampling clock after the command to transmit Only the start time tp of the high-frequency selection signal HSEL varies according to the shifting time ta of the transmission, but the sampling time Ts does not change. As a result, the instruction of the microcomputer 1 has no effect. .

Therefore, since the time delay in this case is only the delay factor of the gate, the delay time is sufficiently small with respect to the frequency fh of the input signal Fh, so that if the error is not affected, the higher the fh for such high frequency measurement The larger the Ts, the greater the precision.

Meanwhile, in the method of the present invention performed by the frequency measuring device of the present invention, as shown in FIG. 3, when the carry CA is searched and CA = 1, the sampling time Ts for the high frequency measurement is serialized in the microcomputer 1; In the process of outputting the high frequency selection signal (HSEL) from the port and then receiving the value counted by the sampling time (Ts) and the counter (5) through the parallel / serial latch (6) and measuring the frequency, in the carry search step If CA = 0, the low frequency selection signal LSEL for low frequency measurement is output for one period of the low frequency input signal Fl, and the serial sampling clock counted to the counter 5 during that period. The sampling frequency fs is transmitted through the parallel / serial latch 6 to measure the frequency.

The operation and effect of the method of the present invention thus constructed will be described with reference to FIGS. 1 and 2 (a) to (e). The carry CA is searched for an interrupt (CA = 1) as shown in FIG. If INT is applied, set CA = 0 and then output the low select signal LSL low (logical "0") to terminate the previous section (section CA = 0).

Thereafter, the load signal LD is output to load the value counted by the counter 5 in the previous section into the parallel / serial latch 6, and then the clock CK is output to output the data of the parallel / serial latch 6. It is transmitted through the data input terminal (ON).

After clearing the counter (5) by outputting the clear signal (CL), the serial port Set the transfer mode, then load the serial port data into a register. After that, the timer operation starts, and the timer time Ta is the time (ta) + Ts &lt; The value is greater than three times the frequency to ensure sufficient time before the end of the 8-bit data output in series.

Serial sampling clock This means the determination of the sampling time (Ts), which means that the serial sampling clock by the transfer command is selected when the transmission rate is selected. Initiates and returns a copy of the.

In this case, the timer interrupt loads the count of the high frequency input signal Fh counted during the sampling time Ts to the parallel / serial latch 6 and outputs the clock CK as shown in FIG. The counter 5 is cleared by receiving data through the data input terminal IN and outputting a clear signal CL.

The next step is to switch the serial port to a mode that only outputs a serial clock for counting the low-frequency input signal Fl, followed by a serial sampling clock. Select the frequency of as the sampling frequency (fs) and then start and return the clock output. When returning, return to the carry search step of FIG. 3, and in this case, CA = 0, so the low-pass selection signal LSEL is output high and the serial sampling clock It is supplied to this counter 5, and it returns after setting CA = 1 to perform the next step. As described above, according to the present invention, since the amount of hardware added to the frequency measurement can be reduced by using the serial port of the microcomputer, it is possible to reduce the size and weight of the device. When using the microcomputer of the high speed command cycle, various clocks ( Frequency) can improve the accuracy and reliability, and can measure the frequency of broadband to increase the performance of the device.

Claims (2)

The microcomputer 1 measures the frequency of the high and low frequency input signals Fh and Fl by providing a sampling pulse or sampling period through the serial port and the frequency of the input signals Fh and Fl under the control of the microcomputer 1. A timing processor (4) which performs the processing, a counter (5) which counts the frequencies of the input signals (Fh, Fl) under the control of the microcomputer (1), and the output value of the counter (5) (1) A frequency measuring device using a serial port of a microcomputer provided with a counter / latch portion (7) composed of parallel / serial latches (6). If the CA is searched for CA = 1, the sampling time Ts for the high frequency measurement is output from the serial port of the microcomputer 1 to the high frequency selection signal HSEL, and then the counter 5 is applied for the sampling time Ts. Receiving the value counted by the parallel / serial latch 6 and measuring the frequency; if CA = 0 in the search step, the low-frequency selection signal LSEL for low-frequency measurement and the low-frequency input signal Fl Serial sampling clock counted by counter (5) during one period of output Frequency measurement method using the serial port of the microcomputer consisting of a process of measuring the frequency received by the sampling frequency (fs) via the parallel / serial latch (6).