JPH02674B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a counter that uses a microprocessor to obtain a count depending on a pulse width.

Conventionally, in order to measure pulse width signals using a microprocessor without using an external hard counter, when the pulse width signal to be measured is input via an input/output interface circuit, the leading edge of the input pulse is It is detected and a register inside the microprocessor is used as a counter to perform counting according to the built-in program. Even in the most simplified version of this program, the time required for one count is quite long, so it is not possible to increase the resolution for pulse width detection. For example, in a counter configured as shown in Figure 1a, the program
It starts, reads the input (IN), determines whether the input is high (High), and if the input is high, increments the internal register by the instruction, and sets the input to low (Low). ) Judgment is made based on instructions as to whether or not the level has been reached. While the input is at a high level, this command is executed one count at a time. In other words, the input is high
The time required for one loop of processing to increment the internal register between levels is the time required for one count, but the number of instructions or states required for this processing is considerably large, resulting in a longer one count time. If the time required for one count is long, the resolution of pulse width measurement cannot be improved. For example, when using Intel's 8080A microprocessor, a minimum of 4 instructions are required, and each count takes about 14.5 μsec. Another method is to write a NOP (no operation) instruction into memory in advance, which does not cause the processor to do any work.
The method of executing this NON instruction when counting the pulse width time and obtaining the count number from the contents of the program counter after counting is completed reduces the time required for one count, but requires a large memory capacity and requires a long pulse width. This method is not suitable for counting time and is not practical.

An object of the present invention is to solve the above problems and provide a counter using a microprocessor.

Hereinafter, the present invention will be explained in detail using the drawings.
FIG. 2 is a conceptual configuration diagram of an embodiment according to the present invention. In FIG. 2, 1 is a microprocessor and its peripheral devices (memory is omitted).
10 is a microprocessor main body, and a bidirectional data bus 13 is outputted from the microprocessor 10 via an address bus 11, a control bus 12, and a bus driver. The microprocessor 10 has an INT terminal that receives an interrupt request, and when it receives an interrupt, it outputs an interrupt recognition signal from the terminal indicating that the interrupt has been accepted. This interrupt recognition signal output terminal () is connected to the interrupt instruction port 14, and this interrupt instruction port 14 is used to save each register of the microprocessor 10, analyze the cause of the interrupt, and respond to the type of interrupt. An interrupt instruction to be transferred to the interrupt processing routine is placed on the data bus (actually, the necessary part is usually executed by hardware and the rest is done by software). An address bus 11, a control bus 12, and a data bus 13 are connected to the input/output interface 15, and chip selection of the input/output interface 15 is performed by a predetermined signal, and under certain conditions (described later). Outputs control signals. Although not shown, the memory includes an address bus 11 and a control bus 12.
A data bus 13 is connected to the microprocessor 10, and necessary program data and the like are input to the microprocessor 10 when necessary. 2 is a pseudo-instruction generation part,
It is constructed of hardware and carries a certain instruction on the data bus 13 so that the program counter of the microprocessor 10 changes sequentially by a constant value. The pseudo-instruction code generator 2 generates instructions that are not ``an instruction that jumps or branches to another program during the execution of the instruction and causes the contents of the program counter to change irregularly'' among the instructions determined by the microprocessor 10. It is configured to generate instructions that are not "instructions that affect registers etc. that are being used during execution." In the example shown in FIG. 2, among the lines of the data bus 13, DB ₀ to
The DB ₆ line is pulled up to the +Vcc power supply with a resistor of about 3 kΩ, and the DB ₇ is connected to common with a resistor of about 8.2 kΩ, forming a machine code of “7F” in hexadecimal notation (this is the accumulator's (This is an instruction to transfer the contents to the storage unit.)
Reference numeral 3 designates an input circuit, into which a pulse width signal to be measured is inputted to an input terminal 31, and selection of detection of a rising edge or a falling edge of the input signal is performed in response to a control signal from an input/output interface 15. In the input/output circuit 3, the input signal line 31 is directly connected to the AND gate 34 via an inverter 36 and to the AND gate 35, and the control signal line 33 from the input/output interface 15 is connected to the AND gate 34 via an inverter 37. It is directly connected to the AND gate 35 via.

The operation of the apparatus of the present invention configured as described above will be explained next. FIG. 3 is a flowchart for explaining the operation of the apparatus of the present invention. First, when you start the program, the microprocessor 10
selects the input/output interface 15 that provides a control signal to the input circuit 3, and opens the AND gate 35 via the input/output interface 15 in order to detect the rising edge of the pulse width signal to be measured (as shown in the frame of the flowchart in Figure 3). Symbol a). Then, it is made interruptible by an instruction (symbol b) and placed in a state of waiting for an interrupt or in a state of executing another program (symbol c). When the pulse width input signal to be measured is input to the input terminal 31 of the input circuit 3, it is output to the output terminal 32 via the AND gate 35 and the OR gate 38, and is output to the output terminal 32 of the microprocessor 10.
Input to the INT terminal as an interrupt request signal (symbol d). Then, the microprocessor 10 immediately outputs an interrupt recognition signal ( ), and the interrupt instruction port 14 receives this and outputs the interrupt recognition signal (
Place the necessary interrupt instructions on top. As mentioned above, the necessary part of the interrupt instruction is transferred to this port 14.
Usually, it is executed by an instruction loaded from a memory, and then executed by an instruction fetched from memory or the like. In this way, it is determined whether the pseudo-instruction has been executed or not.In other words, it is determined whether the interrupt was generated at the rising edge or the falling edge of the signal under test (symbol e), and the pseudo-instruction is executed. If the microprocessor is interrupted at a rising edge, the microprocessor automatically becomes interrupt-disabled. Before moving to the pseudo-instruction execution stage, do the following: First, set the falling edge of the signal under test to the detection state (symbol f),
It is again enabled for interrupts (symbol g) and jumps to a non-existent address in memory (symbol h). and,
An address that does not exist in memory, for example 8000 in hexadecimal
When an address is entered into the program counter, the program counter points to a non-existent address in memory, so no valid instructions are read from memory. Therefore, only the pseudo-instruction set on the data bus 13 is valid, so this pseudo-instruction is executed (symbol i) and the execution of this pseudo-instruction is repeated until the next interrupt occurs. During this time, the increase in the contents of the program counter indicates the number of times the pseudo-instruction has been executed. Now, when a falling edge is detected and an interrupt occurs (symbol j), it is determined whether the pseudo-instruction has been executed again (symbol e), and if it is affirmative, the increment in the contents of the program counter is determined (symbol k). After the return program, the program returns to the next program (symbol l). The time required for one execution of a pseudo-instruction or one count time determines the resolution of pulse width measurement.

As described above, with the conventional soft counter, one count always requires the execution time of several instructions, making it impossible to increase the resolution, but with the device of the present invention, at least one instruction is required. One count time can be shortened to the execution time, and resolution can be increased.

FIG. 4 shows a part of an electrical configuration diagram showing another embodiment of the counter according to the present invention. In this embodiment, the pulse width of the voltage to be measured is changed to obtain a count proportional to the voltage to be measured.
Although not shown in FIG. 4, the microprocessor, its peripheral circuit 1, and pseudo-instruction generating section 2 are the same as those in FIG. 2. 3 is the input circuit, the second
The input circuit 3 is different from the figure. 31 is an input signal line;
32 is an output signal line, 39 is a comparator, 310
is a ramp waveform generator, 35 is a ramp waveform generator 3
This is a signal line that provides 10 start pulses. The input signal line 31 and the output terminal of the ramp waveform generator 310 are input to the comparator 39, and when the output voltage of the ramp waveform generator 310 becomes equal to the voltage to be measured, the output of the comparator 39 is inverted and an interrupt of the microprocessor 10 is generated. Request signal input terminal
Give an interrupt request signal to INT. With the above configuration, from the output signal line 32 of the input circuit 3, the time from the start of the ramp waveform generator 310 until the output of the comparator 39 is inverted is Tx.
Then, Tx is proportional to the measured voltage Ex.
This time Tx can be counted in the same manner as in the previous embodiment to obtain a count proportional to Ex. The operation will be explained below with reference to FIGS. 4 and 5. First, the microprocessor 10 configured as shown in FIG. 2 is started and placed in an interrupt-enabled state (frame symbol a in the flowchart in FIG. 5a). Next, the ramp waveform generator 310 is started to output a ramp waveform voltage (symbol b). Fifth
As shown in FIG. b, the ramp waveform is a linear waveform in which the voltage increases in proportion to time, and the time Tx from when the ramp waveform voltage is generated until it becomes equal to the measured voltage Ex is proportional to Ex. As soon as the ramp waveform generator 310 starts, the microprocessor 10 causes the program to jump to a non-existent address in memory (symbol c). From this jump address, the microprocessor 10 starts executing the pseudo-instruction, and the program counter repeatedly advances until an interrupt occurs (symbol d). When an interrupt occurs, a predetermined interrupt program reads the contents of a program counter provided from the outside (interrupt command port 14, etc.) (number e), passes through a return program (number f), and moves to the next program. A count number corresponding to Tx, that is, the voltage to be measured Ex, can be obtained from the increase in the contents of the program counter (increase from the jump address) obtained during execution of the interrupt instruction. Also in this embodiment, since the time required for one count is short, the resolution of voltage measurement can be increased, which is very useful.

In the above example, the time from when a certain signal is generated until it disappears is here considered as a pulse width signal for convenience.

As described above, according to the counter using the microprocessor according to the present invention, a counting system with high resolution can be realized.

[Brief explanation of drawings]

FIG. 1a is a conventional counter system using a microprocessor, b is a flowchart for explaining its operation, FIG. 2 is an electrical configuration diagram of a counter using a microprocessor according to the present invention, and FIG.
4 is a diagram showing a part of an electrical configuration diagram of another embodiment of the apparatus of the present invention, and FIG. 5 is a flowchart and a waveform diagram for explaining the operation. 1...Microprocessor and its peripheral circuit, 10...Microprocessor main body, 11...
Address bus, 12...Control bus, 13
...Data bus, 14...Interrupt instruction port,
15...I/O interface, 2...Pseudo-instruction generation section, 3...Input circuit.

Claims (1)

[Scope of Claims] 1. A microprocessor, a memory provided in the microprocessor, and a pseudo-instruction code that causes a program counter of the microprocessor to sequentially change by a constant value. - A pseudo-instruction generator placed on the bus, and an interrupt signal that causes the microprocessor to execute the pseudo-instruction while the pulse width signal is being input, and terminates execution of the pseudo-instruction when the pulse width signal disappears. an input circuit for inputting the pseudo-instruction to the microprocessor, the program counter of the microprocessor sets the contents of the program counter of the microprocessor to a non-existing address in the memory before starting execution of the pseudo-instruction; A counter using a microprocessor that obtains a count according to a pulse width signal from the number advanced from the start to the end of execution. 2. It is configured to interrupt the microprocessor at the leading edge of the pulse width signal and start execution of a pseudo-instruction in response to this interrupt request signal, and interrupt the microprocessor again at the trailing edge to end the execution of the pseudo-instruction. A counter using a microprocessor according to claim 1. 3. Execution of a pseudo-instruction is started when the pulse width conversion of the signal under measurement to be converted into a pulse width signal starts, and execution of the pseudo-instruction is ended by interrupting the microprocessor when the pulse width conversion is completed. A counter using a microprocessor according to claim 1.