JPH08328745A - Analog/digital converter - Google Patents

Abstract

PURPOSE: To suppress the performance deterioration of an engine or the like for instance by fetching the output digital signals of a conversion part after prescribed time after a processing part outputs conversion request signals when the abnormality of a completion signal transmission system is detected. CONSTITUTION: An A/D converter 1 reads and decodes command data and channel data for indicating an object sensor in synchronism with inputted clock signals, A/D converts the signals of a specified sensor and outputs a conversion end signal for indicating that A/D conversion is ended to a microcomputer 2. In a normal case, the microcomputer 2 starts the processing of reading an A/D conversion value by the reception of the conversion end signal, however, in the case of the abnormality of a conversion end signal system, since the conversion end signal can not be received, the processing of reading the A/D conversion value can not be started. However, since the microcomputer 2 detects the abnormality of the conversion end signal system by the result of the data reception of a previous time, the microcomputer 2 fetches the A/D conversion value by timer matching interruption after the lapse of the prescribed time from the time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analog / digital converter, and a converter for performing analog / digital conversion,
The present invention relates to a digital conversion device of a type that communicates with a processing unit that takes in and processes a converted digital value.

[0002]

2. Description of the Related Art In recent years, in electronic equipment control systems such as automobile engine control systems, various sensors detect the state of the engine and the running state, and the information from these sensors is processed by a microcomputer to obtain the optimum state. The control for driving the vehicle is performed. Most of the information from these various sensors is an electrical signal, and a digital signal and an analog signal are used. When a microcomputer processes these signals, the digital signal can be directly input to the microcomputer for processing, but in the case of an analog signal, it must be converted into a digital signal before being input to the microcomputer.

An analog / digital converter is used to convert an analog signal into a digital signal, but a plurality of types of analog signals are sequentially converted into digital signals by one analog / digital converter in order to simplify the configuration. A multi-channel type analog / digital converter is often used. A communication line (wiring pattern of printed wiring board, flexible board, conducting wire [lead wire]) for transmitting data etc. is provided between the analog / digital converter and the microcomputer. Various communication systems have been adopted, and SPI (Serial Peripheral Interface) is less likely to cause communication errors such as synchronization errors when controlling automobile engines.
The communication method of the method is often used.

Next, an analog / digital converter using SPI communication will be described with reference to FIG. An analog / digital converter 51 is connected to a plurality of (24 channels in this example) sensors and inputs analog signals from these sensors. Also, since the analog / digital converter 1 communicates with the microcomputer 2,
A clock input terminal A1, a data input terminal A2, a data output terminal A3, and a conversion end signal output terminal A4 are provided, and a clock output terminal B1, a data output terminal B2, a data input terminal B3 on the microcomputer 2 side, respectively.
It is connected to the external interrupt terminal B4.

A clock signal (pulse signal) serving as a synchronizing signal for data communication is input from the clock output terminal B1 to the clock input terminal A1. Further, the conversion command signal (serial signal) from the data output terminal B2 is input to the data input terminal A2, the conversion result signal (serial signal) from the data output terminal A3 is input to the data input terminal B3, and the external A signal indicating that the analog / digital conversion (analog / digital conversion) is completed is input to the interrupt terminal B4 from the conversion end signal output terminal A4.

FIG. 8 is a diagram showing the timings of analog / digital conversion and communication. Next, the timings of analog / digital conversion and communication will be described. When the output signal data of the sensor is required, the microcomputer 52 first converts the command data indicating the conversion instruction and the channel data indicating the target sensor into the analog / digital converter 5.
1 is written into the transmission register for transmission, and these data are output together with the clock signal in synchronization with the clock signal (u1).

The analog / digital converter 51 reads command data and channel data indicating a target sensor in synchronization with an input clock signal, decodes the same, and converts the signal of a designated sensor (channel) into an analog signal. . When the analog / digital conversion is completed, the analog / digital converter 51 outputs the conversion end output terminal A4 to the external interrupt terminal B4 of the microcomputer 52.
A conversion end signal indicating that the analog / digital conversion is completed is output to and the conversion result is written in a transmission register for transmitting data to the microcomputer 52 (u2).

Upon receiving the conversion end signal, the microcomputer 52 transmits a clock signal by interrupt processing (u3). Then, since the conversion result written in the transmission register on the analog / digital converter 1 side is transmitted in synchronization with the clock signal, the conversion result is read in synchronization with the clock signal, and the analog / digital conversion is performed once. And the communication processing is completed (u4).

[0009]

In such a digital converting apparatus, the signal line for transmitting the conversion end signal is conventionally broken, and the end interrupt does not occur (the conversion end signal is not input). In this case, the microcomputer 52 considers that the analog / digital conversion unit 51 is abnormal,
Although the system reset of the analog / digital converter was performed, the system reset does not restore the normal state if the signal line is broken. Therefore, the microcomputer 52 is a fail-safe that controls the engine without a signal from the sensor. Will be controlled. Therefore, in such a case, the vehicle can be driven by the fail-safe control, but the performance (fuel consumption, exhaust gas, traveling ability, riding comfort) and the like deteriorate. An object of the present invention is to prevent the deterioration of the performance of an engine or the like in such a case.

[0010]

In order to solve such a problem, the present invention solves such a problem by converting an analog signal into a digital signal, and connecting the converter with a communication line and outputting from the converter. The conversion unit performs conversion by a conversion request signal from the processing unit and outputs a conversion completion signal to the processing unit after conversion is completed, and the processing unit In an analog / digital conversion device that takes in the digital value from the conversion unit after the conversion completion signal from the conversion unit is input, an abnormality detection unit that detects an abnormality in the completion signal transmission system of the conversion completion signal; When an abnormality of the completion signal transmission system is detected by the abnormality detecting means, a predetermined time after the processing unit outputs the conversion request signal, the output digital signal of the conversion unit is output. And an auxiliary capturing means for capturing the signal.

Further, the abnormality detecting means is characterized in that the conversion request signal is compared with a digital value from the conversion section corresponding to the conversion request signal, and an abnormality is judged based on the comparison result.

[0012]

According to the present invention, when the conversion end signal transmission line for transmitting the conversion end signal is abnormal in the present invention, the analog / digital conversion value is read according to the judgment of the processing section. It is possible to avoid a state where analog / digital values cannot be input due to an abnormality in the transmission line.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the present embodiment, an engine control device for controlling the engine of an automobile will be described as an example, but the present invention can be applied to a device using an analog / digital conversion device other than the engine control device. FIG. 1 is a configuration diagram showing a configuration of an engine control device for an automobile. Various sensors are connected to the engine control device 5, and signals from these sensors are input and processed, and various actuators are controlled to operate the engine in an appropriate state. The sensor includes a digital sensor that outputs a digital signal such as a pulse and an analog sensor that outputs an analog signal such as a voltage value.

The digital sensor includes a rotation angle sensor that outputs a TDC signal indicating the rotation angle of the engine (such as top dead center), a rotation speed sensor that outputs an NE signal indicating the engine rotation speed, and a wheel rotation. There is a vehicle speed sensor that outputs a vehicle speed signal indicating the number. The analog sensors include an intake pipe pressure sensor that detects the pressure in the intake pipe of the engine, a water temperature sensor that detects the water temperature of the radiator, an intake temperature sensor that detects the temperature of intake air, and an oxygen concentration in the exhaust gas. There is an oxygen concentration (O2) sensor, a throttle valve sensor that detects the opening of the throttle valve, and the like.

Reference numeral 3 denotes an input interface for performing a buffering operation or the like for connecting a sensor, which connects a digital sensor and a microcomputer 2 and also an analog sensor and an analog / digital converter (A / D converter) 1 is connected. Reference numeral 1 denotes an A / D converter, which converts an analog signal from the analog system sensor input via the input interface 3 into a digital signal and outputs the digital signal to the microcomputer 2.

Reference numeral 2 denotes a microcomputer, which receives and processes a signal from a sensor and controls actuators provided at various places of the engine to control the engine to operate in a state according to the situation. Reference numeral 4 denotes an output interface for connecting the microcomputer 2 and the actuator, which performs a buffering operation and the like.
The actuator is equipped with, for example, a spark plug for igniting the engine, an injector for injecting gasoline, and a throttle valve in parallel with the throttle valve to control the air amount when the throttle valve is closed (idle rotation). There is an idle speed control valve (ISC valve) etc. to control the number, and if necessary, the microcomputer 2
There are provided drive circuits such as a digital-analog signal converter for converting the digital signal from the above into an analog signal, a booster circuit for boosting the voltage, and a duty conversion circuit for converting the digital signal into a pulse signal having a duty value corresponding to the digital signal.

Next, the details of the analog / digital converter using SPI communication will be described with reference to FIG.
The A / D converter 1 is connected to a plurality of (24 channels [ch] in this example) analog type sensors, and inputs analog signals from these sensors. Further, the A / D converter 1 is provided with a clock input terminal A1, a data input terminal A2, a data output terminal A3, and a conversion end signal output terminal A4 for communication with the microcomputer 2. Clock output terminal B1, data output terminal B
2, connected to the data input terminal B3 and the external interrupt terminal B4. The connection between these terminals should be
If the D / D converters 1 are mounted on the same printed circuit board, they are connected by the wiring pattern of the printed circuit board,
If they are not mounted on the same substrate, they are connected by a flexible substrate or a conductor (lead wire).

A clock signal (pulse signal) which is a synchronizing signal for data communication is input to the clock terminal A1 from the clock output terminal B1. Further, the conversion command signal (serial signal) from the data output terminal B2 is input to the data input terminal A2, the conversion result signal (serial signal) from the data output terminal A3 is input to the data input terminal B3, and From the conversion end signal output terminal A4 to the analog / digital conversion (A /
A signal indicating that the (D conversion) is completed is input.

Next, the conversion and communication operation will be described.
In SPI communication, a clock signal is transmitted only when data is transmitted. In other words, if the microcomputer 2 outputs a clock signal, data communication between the data input terminal A2 and the data output terminal B2 and data input are performed at the same time. Terminal B
Data communication between the data output terminal 3 and the data output terminal A3 is performed by using the clock signal as a synchronization signal. Specifically, the signal level (H level: high voltage level, L level: low voltage level) of the communication line at the time of the fall of the clock signal is set as 1 bit of communication data and is transmitted. According to the desired data, the signal level of the communication line is sequentially switched in synchronization with the clock signal, and the receiving side reads the signal level of the communication line at the falling edge of the clock signal and assembles it into the received data.

For example, a case of transmitting a 4-bit signal "1101" from the microcomputer 2 side to the A / D converter 1 side will be described with reference to FIG. Indicates a clock signal, and the microcomputer 2 side is in a state (H level, L
A pulse signal whose level is changed is transmitted to the A / D converter 1 side. The number of pulses is the same as the bit length of the data to be transmitted, and is predetermined (4 pulses in this example).
In addition, the microcomputer 2 uses the falling edge of the clock signal (t1,
At t2, t3, and t4), the signal level of the data communication line is sequentially controlled to be the signal level “HHLH” () corresponding to the communication data “1101”. On the A / D converter 1 side, when the clock signal falls (t1, t
2, t3, t4) signal level of communication line "H
HLH ”is input, and it is determined that the corresponding data“ 1101 ”is communicated.

In the above description, the A / D from the microcomputer 2 side
Although the case of transmitting to the converter 1 side has been described, when transmitting from the A / D converter 1 side to the microcomputer 2 side, the same operation is performed in synchronization with the clock signal from the microcomputer 2.
Further, since the transmission line from the microcomputer 2 side to the A / D converter 1 side and the transmission line from the A / D converter 1 side to the microcomputer 2 side are separate lines, the clock signal from the microcomputer 2 is If each transmits data in synchronization, bidirectional communication is possible at the same timing.

Next, the format of transmission data will be described. FIG. 4 shows the format of transmission data (16 bits). (A) is the format of transmission data from the microcomputer 2 side to the A / D converter 1 side, and (b) is from the A / D converter 1 side. The format of the transmission data to the microcomputer 2 side is shown. The transmission data from the microcomputer 2 side to the A / D converter 1 side basically includes command data D1 indicating what kind of operation the A / D converter 1 is to perform and which sensor (which channel). Signal A
It is composed of channel data D2 that specifies whether to perform D / D conversion.

The transmission data from the A / D converter 1 side to the microcomputer 2 side are basically conversion result data D3 indicating the conversion result of the A / D conversion and a check code indicating the completion of the A / D conversion. D4 and conversion terminal data D5 indicating which input terminal has the A / D conversion result, that is, which sensor (which channel) has the A / D conversion result. Next, the data transmission / reception processing performed by the microcomputer 2 will be described. Figure 5
3 is a flowchart showing a transmission / reception process performed by the microcomputer 2. This transmission / reception process is executed by interruption at regular time intervals when the vehicle engine is in a driving state.

In step S1, it is judged whether or not the A / D conversion completion signal is received in response to the previous conversion instruction to the A / D converter 1, and if it is received, the process proceeds to step S6 and is received. If not, the process proceeds to step S2. This determination is made based on the presence / absence of an interrupt input of the conversion end signal to the external interrupt terminal B4 (the state of the conversion end flag set when there is an interrupt). In step S2, the A / D conversion value received by the previous transmission / reception process is stored in the memory, and the process proceeds to step S3. In step S3, the conversion terminal data received by the previous transmission / reception process is stored in the memory, and the process proceeds to step S4.

In step S4, the channel data designated in the transmission / reception process two times before is compared with the conversion terminal data input in the previous transmission / reception process. If they match, the process proceeds to step S6. . That is, if there is an abnormality in the conversion end signal system, that is, the end interrupt line which is the communication line between the conversion end signal output terminal A4 and the external interrupt terminal B4, the conversion end signal is not input on the microcomputer 2 side. The designated A / D conversion value is in the input state.

In the present embodiment, this state is matched with the presence / absence of the interrupt input of the conversion end signal and the channel data instructed, and the conversion terminal data input together with the A / D conversion result (data transmission system and A). If the / D converter 1 is normal, the data indicates the same sensor, so these data are in agreement). Then, in step S5, an end signal abnormality flag indicating that the conversion end signal system is abnormal is set, and the process proceeds to step S6.

By the processes of steps S1 to S5, the abnormality detection process of the conversion end signal system is performed. In step S6, an A / D conversion channel is selected, and the process proceeds to step S7. This selection is for designating the sensor that outputs the data required for engine control. In step S7, the channel selected in step S6 is stored in the transmission memory, and the process proceeds to step S8. In step S8, a command instructing the operation to be performed by the A / D converter 1 is selected and stored in the transmission memory, and then the step S8
Go to 9. The channel selection and command selection of these sensors are selected according to an engine control program stored in advance in a memory. Then, step S9
Then, the selected channel and command are transmitted to the A / D converter 1 to cause the A / D converter 1 to perform operations such as A / D conversion, and the process proceeds to step S10. These steps S6
From step S9 to step S9, instruction processing such as A / D conversion operation for the A / D converter 1 is performed.

In step S10, it is determined whether the conversion end signal system is abnormal. If the conversion end signal system is abnormal, the process proceeds to step S11. If not, step S1.
Move to 2. This determination is made based on the end signal abnormality flag set in step S5. In step S11,
After a certain time from the current time, the timer coincidence interrupt operation for performing the process of reading the A / D converted value of the A / D converter 1 is started, and the process proceeds to step S12. In other words, an interrupt is made so that the A / D conversion value of the A / D converter 1 is read after a fixed time (after the time when the A / D conversion process of the A / D converter 1 is considered to have surely completed). Processing is set. Step S
At 13, the conversion end flag is reset and the transmission / reception process ends.

FIG. 6 is a diagram showing the timing of A / D conversion and communication. Next, the operating state of the A / D converter of this embodiment when the conversion end signal system is abnormal will be described. The operating state of the A / D converter in the normal state is the same as the state shown in FIG. When sensor output signal data is required, the microcomputer 1 first sends command data D1 indicating a conversion command and channel data D indicating a target sensor.
2 and 2 are transmitted to the A / D converter 1, so they are written in the transmission register. Then, these data are synchronized with the clock signal and output together with the clock signal (w1).

The A / D converter 1 reads and decodes the command data D1 and the channel data D2 indicating the target sensor in synchronization with the input clock signal, and A / D converts the signal of the designated sensor. When the A / D conversion is completed, the A / D converter 1 outputs the conversion end signal output terminal A
4 outputs a conversion end signal indicating that the A / D conversion is completed to the external interrupt terminal B4 of the microcomputer 2 and the microcomputer 2
In order to transmit the data to, the conversion result is written in the transmission register (w2).

If the conversion end signal is normal, the microcomputer 2 starts the process of reading the A / D conversion value by receiving the conversion end signal. However, if the conversion end signal system is abnormal, the conversion end signal cannot be received. , The process of reading the A / D converted value cannot be started. However, in the case of the present embodiment, the microcomputer 2 receives the previous data (A /
The A / D conversion result for the D conversion request is input. )
Since the abnormality of the conversion end signal system is detected from the result of, the microcomputer 2 waits for a predetermined time from that time (w3
Up to w4) fetch the A / D converted value by the timer coincidence interrupt.

As described in detail above, according to the present embodiment, when the conversion end signal system is abnormal, the microcomputer 2 is
The A / D conversion value is read and processed by its own judgment regardless of the conversion end signal from the / D converter 1. Therefore, according to this embodiment, although the A / D conversion itself is normally performed, the control using the A / D converted value can be performed when the conversion end signal system is abnormal.

[0033]

As described in detail above, according to the present invention, when A / D conversion itself is normally performed, A
Even if an abnormality occurs in the part that does not affect the A / D converted value, the normal A / D converted value can be used for control as much as possible. Control can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram of an engine control system

FIG. 2 is a block diagram showing details of an A / D conversion unit.

FIG. 3 is a state diagram showing states of signals.

FIG. 4 is a diagram showing a format of transmission data.

FIG. 5 is a flowchart showing a transmission / reception process performed by the microcomputer 2.

FIG. 6 is a diagram showing timings of A / D conversion and communication.

FIG. 7 is a block diagram of an A / D converter using SPI communication.

FIG. 8 is a diagram showing timings of A / D conversion and communication.

[Explanation of symbols]

 1 ... A / D converter 2 ... Microcomputer 3 ... Input interface 4 ... Output interface 5 ... ... Engine control devices

Claims (2)

[Claims] 1. A conversion unit which converts an analog signal into a digital signal, and a processing unit which is connected to the conversion unit by a communication line and takes in and processes an output digital signal output from the conversion unit. The conversion request signal from the processing unit performs conversion and outputs a conversion end signal to the processing unit after the conversion ends, and the processing unit inputs the conversion end signal from the conversion unit and then outputs from the conversion unit. In an analog / digital conversion device that takes in a digital value, abnormality detection means for detecting an abnormality in the end signal transmission system of the conversion end signal, and when the abnormality detection means detects an abnormality in the end signal transmission system, And a supplementary capturing means for capturing an output digital signal of the conversion unit after a predetermined time has elapsed after the processing unit outputs the conversion request signal. Analog / digital converter. 2. The abnormality detecting means compares the conversion request signal with a digital value from the conversion section corresponding to the conversion request signal, and judges an abnormality based on the comparison result. Item 1. The analog / digital conversion device according to item 1.