Electrical computers and digital data processing systems: input/ – Input/output data processing – Direct memory accessing
Reexamination Certificate
2001-12-20
2004-07-06
Shin, Christopher B. (Department: 2182)
Electrical computers and digital data processing systems: input/
Input/output data processing
Direct memory accessing
C710S052000, C709S250000, C709S212000, C711S165000
Reexamination Certificate
active
06760789
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on Japanese Patent Application No. 2001-2615 filed on Jan. 10, 2001 the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microcomputer having a function for receiving data and a processing method for received data.
2. Description of the Related Art
It is now an ordinary matter that data communications are conducted among a plurality of microcomputers. For example, a vehicle is usually loaded with electronic control units (hereinafter referred to as ECUs) in the engine drive system, running safety system, entertainment system and other various functional systems to constitute thereby a mobile computer system. Therefore, data communications among such ECUs are effective to realize the optimum control in various systems of a vehicle. For such data communications, there is provided a constitution in which the ECUs loaded in various functional systems are mutually connected via a network such as intra-vehicle LAN (Local Area Network).
SUMMARY OF THE INVENTION
As shown in
FIG. 4
, for example, an ECU
100
is loaded in a vehicle. An ordinary ECU is provided with an input/output circuit and a microcomputer but it is also provided for network communication with a driver
110
connected to a LAN
90
as one of the input/output circuit. A microcomputer
120
of the ECU
100
includes a CPU
130
, a ROM
140
, a RAM
150
and a LAN block
160
. The LAN block
160
has a function to fetch communication data from the intra-vehicle LAN
90
via a driver
110
and moreover to transmit the communication data to the intra-vehicle LAN
90
.
Reception of the communication data via the LAN block
160
will be explained in further detail. The LAN block
160
is provided with a message box
160
a
, a protocol controller
160
b
and a filter circuit
160
c
. In this example, the message box
160
a
has sixteen blocks. The communication data of the intra-vehicle LAN
90
is constituted of identification information (hereinafter referred to as “ID”) indicating an address of transmission source ECU and a kind of data or the like and communication data itself and thereby it is called a message. The message box
160
a
has a structure to store the ID and data itself in pair. In
FIG. 4
, each message box
160
a
is given the numbering from “0” to “15” for the convenience of explanation.
A message fetched by the driver
110
from the network is first decoded by the protocol controller
160
b
and is selected by the filter circuit
160
c
. The filter circuit
160
c
is a logic circuit to select the message based on the ID explained above. Thereby, the message is stored in any one of the message box
160
a
given the numbering from “0” to “15”.
The CPU
130
reads the message from the message box
160
a
on the basis of an interruption signal indicating message reception from the LAN block
160
and stores this message, for example, to the RAM
150
in order to execute the process depending on such message. However, the CPU
130
does not operate depending on only the message from the intra-vehicle LAN
90
and operates depending on the signals from the other input circuits. Accordingly, the CPU
130
preferentially executes the process which is in the higher real-time processing level by conducting the process change-over operation such as the task dispatch or the like. As a result, when the process priority of the message received is relatively lower, even if the interruption signal is received, the message cannot always be obtained immediately from the message box
160
a.
Meanwhile, a communication rate has been much improved in the intra-vehicle LAN
90
. For example, this communication rate has reached several Mbps. Therefore, here is generated an event that the next message is received before the CPU
130
fetches a message from the one message box
160
a
and thereby the next message is over-written in the message box
160
a
during the fetching process of message. That is, the CPU
130
accidentally generates, in a certain case, a failure of the message fetching process. Such failure of the message fetching process is not desirable from the viewpoint of performance of the CPU
130
because it surely results in deterioration of control performance thereof. For prevention of the failure of the message fetching process, it is very effective that a plurality of message boxes are assigned, for example, to store groups of the messages having comparatively lower process priority and the messages are stored in the vacant storage areas among a plurality of message boxes. In
FIG. 4
, thirteen message boxes
160
a
which are identified with the numbering from “1” to “13” are assigned, for example, for the groups of messages having comparatively lower process priority, the messages are selected by the filter circuit
160
c
and the selected messages are stored in the vacant message boxes
160
a
among the thirteen message boxes
160
a
. Thereby, if a delay time is generated in the read operation of message by the CPU
130
, generation of the failure in the message fetching process is reduced because the thirteen messages in maximum are stored.
However, since the number of message boxes is restricted, the message boxes are probably used completely when the received messages are spread to various kinds of data and the communication rate is comparatively higher. Here, it is considered to increase the number of message boxes to provide a countermeasure, but it is actually difficult to realize because of the following reasons. The required number of message boxes is different depending on the frequency of message reception and moreover on the number of messages as the reception object. Accordingly, the structure of the LAN block becomes large in size and thereby a size of the ECU becomes large when the there is no limit to the number of message boxes used for a particular application. In addition, expansion in size of the message box is related only to expansion of a communication function and does not make any contribution to improvement of flexibility of a microcomputer itself. Therefore, such expansion of the message box results in an increase in manufacturing costs.
An object of the present invention is to overcome the problems explained above.
Another object of the present invention is to reduce generation frequency of failure in the communication data fetching process.
The other object of the present invention is to eliminate occurrence of such failure in the communication data fetching process.
The still other object of the present invention is to reduce generation frequency of failure in the communication data fetching process without any expansion of storage region of a data storage means, for example, a message box.
According to a profile of the present invention, a microcomputer is provided with a communication means, a data storage means and a process executing means. Moreover, a transfer means transfers communication data stored in the particular storage region of the data storage means. A transfer destination is selected to a temporary storage means which is used by the process executing means. This transfer means transfer the communication data directly without passing the process executing means in a manner that the storage region of the transfer destination is never overlapped. The process executing means basically reads the communication data from the data storage region to execute the processes based on the relevant communication data but executes the processes based on the communication data stored in the particular storage region depending on the communication data stored in the temporary storage means. Since the transfer process is executed without the process executing means, the transfer process can be done independent of various processes executed by the process executing means. Moreover, since communication data is transferred without any overlapping of the storage region in the transfer destination, over-writing of communicatio
Fujita Yoichi
Matsuda Hiroshi
Matsuoka Toshihiko
Denso Corporation
Posz & Bethards, PLC
Shin Christopher B.
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