JPH0221302A - Output method for pulse width modulation signal - Google Patents

Abstract

PURPOSE:To realize the highly accurate modulation of the pulse width together with reduction of the cost by using only an internal timer to output a pulse width modulation signal and using no external timer. CONSTITUTION:When a CPU 1 sets a prescribed time at an internal timer 3, the timer 3 applies the interruptions to the CPU 1 in said fixed time cycle. The CPU 1 outputs a signal to an output part 6 to turn on the output of the part 6 concurrently with reception of an interruption based on a duty ratio command given from an input device 2. At the same time, the CPU 1 sets the time point at a comparison OUT register 4 to turn off the output of the register 4. A comparison part 5 compares the lapse time of the timer 3 with the OFF time of the register 4. If the coincidence is obtained between both times, a signal is outputted to the part 6 to turn off the output of the part 6. Thus the part 6 outputs a pulse width modulation output signal in response to the duty ratio command received from the device 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pulse width modulation signal output method for a control device using a microcomputer having an internal timer and a conveyor-out function.

[Prior art]

Conventionally, as a method for outputting a pulse width modulated signal in a control device equipped with a micro combinator, there has been a method using an external dedicated counter or a method using an internal timer.

For example, as shown in FIG. 4, a method of providing a dedicated external counter is to provide a dedicated external counter 42 external to the CPU 41, and the CPU 41 controls the external counter 42 by a pulse width modulation factor signal from an input device 43. The pulse width is set so that an output signal with a predetermined duty ratio is obtained, the output is turned on according to a command from the CPU 41, and the output is turned off after the set pulse width has elapsed. As a result, a pulse width modulation signal corresponding to the input signal from the input device 43 is output.

Furthermore, as shown in FIG. 5, for example, a method using an internal timer calculates the time for turning the output ON and OFF based on a pulse width modulation factor signal from an input device (not shown).
By operating an internal timer using this ON and OFF calculation time, a pulse width modulation signal corresponding to the signal from the input device is output.

[Problem to be solved by the invention]

However, in the conventional pulse width modulation signal output method described above, when using an external counter, there is a problem that the cost increases due to the use of the external counter, and even when using an internal timer, if the duty cycle is short, the calculation This was not a technically satisfactory method because of the problems of increased frequency and decreased accuracy.

The present invention has been made in view of the above points, and eliminates the drawbacks of the conventional pulse width modulation signal output method, such as high cost and poor accuracy, and uses an internal timer and provides a highly accurate duty output. An object of the present invention is to provide a method for outputting a pulse width modulated signal.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides a control device using a microcomputer with a conveyor-out output function, in which an internal timer of the microcomputer generates an interrupt at a constant cycle, and a program that turns on the output at that time. A pulse width modulation signal output method was constructed by providing a program that stores the OFF time in the conveyor out register.

[Effect]

By configuring the pulse width modulation signal output method as described above, a program that generates an interrupt at a fixed period using an internal timer, turns on the output at that time, and stores the OFF time in the conveyor out register. The OFF time is set by , and the output is turned OFF when the internal timer reaches the OFF time, so it is ON at a certain period and OFF after a predetermined period of time.
A pulse width modulated signal having a so-called predetermined duty ratio can be outputted with high precision.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a functional block diagram of a control device to which the pulse width modulation signal output method of the present invention is applied. 10 is a microcomputer, which has an internal timer and a conveyor out function, such as MSM93 manufactured by Oki Electric Industry Co., Ltd.
Use H001 (product name). CPUI uses internal timer 3
This includes a program that generates an interrupt at a constant period and turns on the output of the output section 6 at that time, and a program that stores the time for turning off the output in the humpair out register 4. The output section 6 is connected to the microcomputer 10 output port OP.

By setting a predetermined time in the internal timer 3 using the CPU, the internal timer 3 interrupts the CPU at the cycle of this predetermined time. In response to a duty ratio command from the input device 2, the CPU outputs a signal to turn on the output to the output unit 6 at the same time as the interrupt occurs, and sets a time to turn off this output in the conveyor out register 4. The comparison section 5 compares the elapsed time of the internal timer 3 and the OFF time of the conveyor out register 4, and if the elapsed time of the internal timer 3 matches the OFF time, the output section 6
A signal is output to turn off the output. As a result, the output section 6 can output a pulse width modulated output signal according to the duty ratio command from the input device 2. The above operation will be explained in detail below using FIG. 2.

FIG. 2 is a diagram showing a timing chart when an output ON is outputted at a level H' (high) output at a cycle of 2 mS to the boat output used for conveyor out of the CPUI. The internal timer 3 has a length of 16 bits and is incremented every 1 μs, and generates an interrupt upon overflow. Here, when setting the output a1 of the output port OP at the timer interrupt, and setting the complement F830H of 2000 μs to the internal timer 3, and setting the duty output to 25%, 500
Set 7ZS (01F4H)+F830H-FEOCH in conveyor out register 4.

If this is done at ■ in Figure 2, the internal timer 3 and conveyor out register 4 match at ■ after 500 μs, and the output of the output port OP becomes "0".
When resetting , the same operation will be repeated if the duty is not changed for 08 hours. When the duty time is changed to 40% (FCEOH) by the timer interrupt at the next time ■, by rewriting the conveyor out register 4, the output of the output port OP becomes “O” at the timing of ■ to 40%.
The output waveform of the output boat OP obtained when the duty output of Often, you only need to set it once if you don't need to change it.

FIG. 3 is a flowchart showing the flow of the above processing performed by an interrupt of an internal timer. An interrupt is generated by the internal timer, and it is determined whether or not internal timer 3 has overflowed (step 101). If it has not overflowed, the conveyor out interrupt request flag is reset (step 102), and if it has overflowed, it is output. Change the boat OP by '1' step 103), internal timer 3
Set 2mS to step 104), then judge whether the ON time (time to turn off the output) has changed or not (step 105), if not, repeat the above process, and if it has changed, turn the conveyor out. Set the ON time in register 4.

〔Effect of the invention〕

As explained above, the pulse width modulation signal output method of the present invention performs the pulse width modulation signal output using only the internal timer without using an external timer, so it is possible to reduce costs, and
High accuracy achieved by using the conveyor out function
This has excellent effects such as making it possible to perform pulse width modulation.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram of a control device to which the pulse width modulation signal output method of the present invention is applied, FIG. 2 is a timing chart for explaining the operation, FIG. 3 is a flowchart showing the flow of processing, and FIG. 4 5 is a diagram showing a configuration example of a pulse width modulation signal output device using a conventional external count.
The figure is a diagram for explaining a conventional method of outputting a pulse width modulated signal using an internal timer. In the figure, 1...CPU, 2...Input device, 3...
...Internal timer, 4...Conveyor out register,
5...Register, 6...Output section, 10...
microcomputer. Ne1ri gII-Pulse D5LIJIi [Brown Shilσmasu!
Figure 4

Claims (1)

[Claims] In a control device that is equipped with a microcomputer having an internal timer and a conveyor-out function and outputs a pulse width modulation signal, the internal timer generates an interrupt at a fixed period to turn on the output, and the conveyor-out function turns on the output. A pulse width modulation signal output method characterized by turning OFF.