JPH1047151A - Automotive electronic control unit - Google Patents

Abstract

(57) [Problem] To provide a logic for maximizing the use of existing resources and using one serial I / F for various purposes according to the operation state of an electronic control device. An electronic control unit for a vehicle equipped with a nonvolatile memory capable of being serially connected to a CPU having at least one serial I / F.
A serially connectable object other than the nonvolatile memory 8 is connected in parallel to F9, and the communication object is switched by time sharing for each operation period of the electronic control device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an automobile, and more particularly, to serial communication of an electronic control device.

[0002]

2. Description of the Related Art Conventionally, in an electronic control unit for a vehicle, it is necessary to save correction data for correcting mechanical differences or aging deterioration of mechanical parts or fault detection information data during running even after an ignition key is turned off. This was realized by using a backup RAM. However, since data is easily destroyed due to a dead battery or a battery being removed, an example of using a non-volatile memory for storing data has recently become popular. In this case, it is necessary to newly connect a dedicated memory, and serial connection is technically easier than bus connection due to the problem of the number of connection lines (for example, Japanese Patent Application Laid-Open No. 5-225049). On the other hand, a CPU incorporated in an electronic control unit for a vehicle is called a one-chip CPU, and in most cases, an arithmetic unit, a memory unit, and a peripheral function unit are incorporated in one IC.

As a result, peripheral functions are naturally restricted, and occupation of the serial I / F for the non-volatile memory itself has caused an increase in cost.

[0004]

FIG. 2 shows the system configuration of the above problem. To connect an external communication device such as a diagnostic monitor or a development tool, a peripheral IC called a serial communication module must be newly added. In addition, there is a problem that the serial communication module has to rely on an external bus connection.

It is an object of the present invention to provide a logic that makes the most of existing resources and uses one serial I / F for various purposes according to the operation state of an electronic control unit.

[0006]

According to the present invention, there is provided an electronic control unit for a vehicle having a nonvolatile memory which can be serially connected to a CPU having at least one serial I / F. This can be achieved by connecting objects that can be serially connected in parallel and switching communication objects by time sharing for each operation period of the electronic control device.

Normally, data access to the nonvolatile memory is performed during an initialization period for loading data from the nonvolatile memory to the RAM and for a termination period for saving data from the RAM to the nonvolatile memory. On the other hand, access to the external communication device is performed. Since it is the active run period when the electronic control unit is controlling the vehicle, it is possible to use one serial I / F for time sharing by constructing logic to operate both programs without interference. And resources can be used effectively.

[0008]

FIG. 1 shows an embodiment of the present invention.

The electronic control unit 1 for a vehicle includes a one-chip CPU 3 including a volatile memory (RAM) 3a and a serial communication module 3b, a program and data storage memory (ROM) 4, a constant voltage power supply circuit 5, and an input signal processing circuit. 6
And an output signal processing circuit 7, a serial connection type nonvolatile memory (EEPROM) 8, and an external communication I / F circuit 9. Here, the constant voltage power supply circuit 5 has two primary input terminals, and the ignition SW 10 and the battery 11 are connected. A battery 11 is connected to the opposite side of the ignition switch 10. The input signal processing circuit 6 and the output signal processing circuit 7 are each connected to each sensor, SW or actuator of the vehicle. In particular, 12 is an input signal for monitoring the state of the ignition switch 10, 13 is an enable signal for the nonvolatile memory 8, 16 is an enable signal for the external communication I / F circuit, and 15 is a control signal for the constant voltage power supply circuit 5. . The control signal 15 controls the power supply on the side directly connected to the battery. In other words, the operation of the constant voltage power supply circuit 5 is as follows. When the ignition SW 10 is turned on, the constant voltage is applied as the power supply voltage of the one-chip CPU 3, and when the CPU is reset and started, the control signal 5 becomes active, and Is also supplied. On the other hand, ignition SW
When the switch 10 is turned off, the primary power supply from the ignition switch 10 is cut off, but the power supply on the battery direct side is alive and the CPU 3 continues to operate. However, when a certain time has elapsed after the ignition switch is turned off, the CPU 3 issues a
Is deactivated, the power supply on the side directly connected to the battery is also stopped, and the electronic control unit 1 for the vehicle is completely stopped. Here, the certain time is usually set to be equal to or longer than the data transfer time from the volatile memory (RAM) to the nonvolatile memory (EEPROM).

On the other hand, reference numeral 14 denotes a diagnostic device serially connected externally to the electronic control unit 1 for the vehicle, which monitors the operating status of the electronic control unit for the vehicle or internal data.
Used for changes and the like. Also, this may be the case of various devices at the time of development. Next, an operation transition when focusing on communication will be described with reference to FIG. In the present embodiment, the operation state of the electronic control unit 1 is divided into three phases. That is, an initialization phase for executing an initialization process after a reset start, an active run phase for receiving an input from a sensor and controlling the actuator based on a calculation result thereof, and a termination phase for detecting that the ignition SW is turned off and performing an end process. .

Next, an operation flowchart in each phase will be described with reference to FIG.

Steps 1 to 5 correspond to the initialization phase.

When the ignition switch 10 is turned on, the electronic control unit 1 itself is reset and starts from the position of step 1. Thereafter, in step 2, initialization of registers and ports of the CPU 3 and in step 3 initialization of the volatile memory (RAM) 3 a are performed. Subsequently, in step 4, the communication protocol is initialized. In this case, communication is performed with a nonvolatile memory (EEPROM), and for example, a synchronous mode, a baud rate of 1 MBPS, and a transfer data size of 16 bits are selected as the protocol. After the initial setting of the communication protocol, in step 5, nonvolatile memory (EEPROM)
Activate the chip enable signal 13 of the nonvolatile memory (EEPROM) 8 to the volatile memory (RAM) 3
Data transfer to a is started. At this time, the external communication I /
The enable signal 16 of the F circuit automatically becomes inactive. After step 5 is completed, the process proceeds to step 6, where the state of the ignition switch is checked. If on, jump to step 7; if off, jump to step 10.

Steps 7 to 9 correspond to the active run phase.

In step 7, the original processing of the vehicle control device for taking in the input of the sensor and controlling the actuator based on the calculation result is performed. However, the first time the active run phase is entered to establish communication with the external diagnostic device 14 in parallel, the communication protocol is reset and the enable signal 16 of the external communication I / F circuit is set in step 8.
Activate At this time, the nonvolatile memory (EE
The chip enable signal 13 of the PROM 8 becomes inactive. In this case, communication with an external diagnostic device is performed. As a protocol, for example, asynchronous mode, baud rate 9.6K
For the BPS and data format, start bit 1, data bit 8, and stop bit 1 are selected. Thereafter, communication is started in step 9. In this phase, the processing from step 6 to step 9 is repeated until the state of the ignition switch 10 changes.

Steps 10 to 12 correspond to the termination phase. First, at step 10, the communication protocol is reset. In this case, the volatile memory (RA
M) to a non-volatile memory (EEPROM), and is basically the same as the setting of the initialization phase. After this setting, in step 11, the chip enable signal 13 of the non-volatile memory (EEPROM) 8 is made active, the enable signal 16 of the external communication I / F circuit is made inactive, and data transfer is started. Thereafter, in step 12, the program itself performs a permanent loop process and stops the power supply to the electronic control unit 1 according to the description.

As described above, the serial I / O
By changing the set value of F and the chip enable signal, one serial I / F can be used for a plurality of purposes. In the present invention, by further subdividing the phase,
OM access is also possible.

FIG. 5 shows another embodiment. In this embodiment, one serial communication module 3b built in the CPU 3 is used for connection to the nonvolatile memory (EEPROM) 8 and connection to the output signal processing circuit 7. The output signal processing circuit 7 referred to in this embodiment has a serial input and a parallel output with a latch.
This is a circuit configuration often used when the number of output ports of U is insufficient. For these two objects, the chip enable signal 13 of the nonvolatile memory (EEPROM) 8 and the enable signal 17 for the output signal processing circuit 7 are prepared to activate the nonvolatile memory (EEPROM) 8 in the initialization phase and the termination phase. In the active run phase, the output signal processing circuit 7 is activated, and both communication targets are used properly. Further, instead of the serial connection type output signal processing circuit 7, a serial connection type input signal processing circuit may be connected. According to this embodiment, the number of input / output ports of the CPU can be reduced,
This can contribute to cost reduction of the CPU itself.

[0019]

According to the present invention, it is possible to provide a logic for selectively using one serial I / F for various purposes according to the operation state of the electronic control unit.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment according to the present invention.

FIG. 2 is a block diagram of the system in question.

FIG. 3 is a communication operation transition diagram of one embodiment according to the present invention.

FIG. 4 is an operation flowchart of an embodiment according to the present invention.

FIG. 5 is a block diagram of another embodiment according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electronic control device for vehicles, 2, 3b ... Serial communication module, 3 ... CPU, 3a ... RAM, 4 ... ROM, 5
... constant voltage power supply circuit, 6 ... input signal processing circuit, 7 ... output signal processing circuit, 8 ... EEPROM, 9 ... external communication I / F circuit,
10: ignition SW, 11: battery, 12: ignition SW monitor input, 13: nonvolatile memory enable signal, 14: external diagnostic device, 15: constant voltage power control signal, 16: external communication I / F circuit enable signal.

Claims (2)

[Claims] An electronic control unit for a vehicle equipped with a nonvolatile memory serially connectable to a CPU having at least one serial I / F, wherein the nonvolatile memory and an external communication device are arranged in parallel with the serial I / F. And an electronic control unit for a vehicle, wherein a communication target is switched every time the electronic control unit operates. 2. An electronic control unit for a vehicle having a non-volatile memory serially connectable to a CPU having at least one serial I / F, wherein the serial I / F has an input which can be serially connected to the non-volatile memory. An electronic control unit for an automobile, wherein output modules are connected in parallel, and a communication target is switched for each operation period of the electronic control unit.