JP2003122707A - Electronic equipment with i2c bus and bus control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce influence to be exerted on operating speed of a system by dispensing with NACK monitoring of a device by a host control part and to make data re-transmission to the device be promptly performed. SOLUTION: When an answer of NACK is received from a slave device at a transmitting destination in the case of transmitting I2C (I squar C) data from the host control part 2 to any of slave devices 5-1 to 5-n via an I2C control part 3, the answer is detected by a NACK monitoring part 7, a stop condition signal is generated by a generating circuit 6 based on it and data transmission communication with the transmitting destination is forcibly terminated. In addition, the host control part 2 is informed of NACK by a NACK informing circuit 8 and made to start re-transmission of the I2C data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device having an I2C bus and a bus control method, and more particularly to a slave device to a NACK (negative ackno).
The present invention relates to an electronic device and a bus control method in which the upper control unit does not have to monitor the (wledgement: negative response).

[0002]

2. Description of the Related Art For example, mobile phones have become multi-functional, and in addition to the original telephone functions, packet communication functions, mail communication functions, Internet (in
ternet) models with features such as have appeared. In addition, there is also a model in which a small camera is attached to the main body so that the surrounding scenery photographed by this camera and one's own face image can be sent to a communication partner. In such a mobile phone, the entire control is performed by a CPU (Central Processing Unit: C
An I / O device for communication (Input / Output device)
), A timer section, a camera section (for example, a CCD)
Image sensor: charge coupled device imagesenso
r) and other peripheral devices are controlled.

As one of buses connecting the peripheral devices and the control unit as described above, there is an "I2C (I square C) bus" which is most suitable for a mobile phone or the like. This I
The 2C bus was developed by Philips and is characterized by the fact that it requires only two lines to compose the bus, so there is a demand for high-density mounting and space saving, such as for mobile phones. Suitable for equipment that has I2
A plurality of slave devices are connected to the C bus, and a lower control unit for managing a plurality of peripheral devices (hereinafter referred to as slave devices) is connected between the I2C bus and the upper control unit.

An I2C control unit is provided between the upper control unit and the slave device, and data (I2C data) from the upper control unit is sent to the designated slave device through the I2C control unit. At the time of this transmission, data of the same content is continuously transmitted four times, and I2C data is surely transmitted. When the data has been transmitted four times, the slave device sends an ACK (acknowledgeme
nt: acknowledgment or confirmation notification or NACK (negative a)
(cknowledgement: negative acknowledgment) is returned and notified to the upper control unit via the I2C control unit. If it is ACK, the communication ends as if the data was successfully received at the slave device.

On the other hand, in the case of NACK, a signal called a stop condition (a signal notifying the completion of transmission data) specified by one of the I2C bus standards from the upper control unit is sent from the upper control unit as NACK.
Is sent to the slave device that issued the command, and the communication between the upper control unit and the slave device is once terminated. Then, the same data as when the transmission failed is continuously retransmitted four times. In response to this transmission, the communication ends if an ACK appears, but if a NACK is returned again, the stop condition occurs → retransmission is repeated until an ACK appears.

There are various proposals regarding bus control. For example, in Japanese Unexamined Patent Publication No. 56-23056, a response monitor circuit is connected to a common bus, and after a request signal requesting data transfer is output from the request instruction circuit to the common bus, retry of data transfer is repeated and preset. When the retry request response is not canceled within the specified time, the response monitor circuit generates an abnormality notification signal. System initialization can be prevented by initializing the time monitoring circuit based on this abnormality notification signal.

Further, in JP-A-8-84205,
When there is no response from the call charge management device while the connection of the call charge management device to the exchange is detected, in order to promptly notify the abnormality occurred in the call charge management device and to speed up recovery When the number of times of no response reaches a certain number of times, an abnormality flag (flag) is set, and based on this, an alarm lamp is turned on in the exchange or the call charge management device.

[0008]

However, according to the conventional electronic equipment and bus control method, the NA of the slave device is
The monitoring of CK is performed by the host controller, and if NACK cannot be monitored due to system busy or the like, communication may continue indefinitely and data may not be normally transmitted. Further, the slave device is monitored (detection of ACK or NACK) by the upper control unit. When the NACK occurs, the stop condition is generated by the upper control unit, and data is retransmitted after the communication is finished. , It may reduce the operating speed of the system. Furthermore, since I2C data is always transmitted the same content four times, it takes four times to complete the communication even if the communication environment is good and only one transmission is required. ing.

Further, in Japanese Unexamined Patent Publication No. 56-23056, after repeated data transfer retries, a state in which data is not transferred continues until it is detected that the retry request response is not canceled within a preset time. Therefore, it takes a considerable amount of time to recover the system. Further, in Japanese Patent Laid-Open No. 8-84205, an abnormal flag does not occur until the number of times of no response from the call charge management device reaches a certain value, and thus it takes a considerable time to recover the system. .

Therefore, an object of the present invention is to eliminate the need for the NACK monitoring of the device by the host controller, reduce the influence on the operating speed of the system, and quickly retransmit the data to the device. It is to provide a bus control method.

[0011]

In order to achieve the above-mentioned object, the present invention has, as a first feature, a high-order control unit which manages the whole and is a data transmission source, and the above-mentioned high-order control unit. One or more devices for receiving data and I2C connected to each of the one or more devices
A bus, a lower control unit connected to the I2C bus and controlling the one or more devices under the control of the higher control unit, and the device receiving the data are NAC.
When K is returned, a stop condition generation circuit that generates a stop condition signal for forcibly ending the transmission process of the data based on this NACK; and a stop condition generation circuit that monitors the occurrence of the NACK and detects the NACK when the NACK is detected. NA that notifies the upper-level control unit that the device is in the NACK state and prompts retransmission of the data
Provided is an electronic device including CK monitoring means.

According to this configuration, when the NACK monitoring means detects that a NACK response has been received from the device when data is sent from the upper control unit to the device, the stop condition generating circuit based on this detects the stop condition. A signal is generated, the process of data transmission is forcibly ended, the upper control unit is notified of the NACK state, and data transmission is re-executed. NA
Since the CK monitoring is performed by the lower control unit, it is not necessary to monitor the device status by the upper control unit, the burden on the upper control unit is reduced, and the influence on the operating speed of the system is reduced. Then, the NACK state is released by the generation of the stop condition signal, and the preparation for retransmission is started, so that the data can be retransmitted quickly.

In order to achieve the above-mentioned object, the present invention has a second feature that data is transmitted from a higher-order control unit to a designated device via an I2C bus, and the device that has received the data enters a receiving state. ACK or NACK depending on
In the bus control method of returning the data to the upper control unit and retransmitting the data from the higher control unit to the device in response to the NACK, the transmission process of the data is forcibly terminated when the NACK occurs. A bus control method is provided, wherein a stop condition signal for causing the device is generated and transmitted to the device, and the data is transmitted again to the device based on the occurrence of the NACK.

According to this method, when the device to which the data is transmitted returns NACK, a stop condition signal is generated to terminate the communication, and the data is retransmitted from the upper control unit. Therefore, since the NACK monitoring is performed by the lower control unit, it is not necessary to monitor the state of the device side by the upper control unit, and the burden on the upper control unit is reduced, so that the influence on the operating speed of the system is reduced. To be done. Furthermore, since the preparation for retransmission is started by the generation of the stop condition signal, the data can be retransmitted quickly.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an electronic device according to the present invention. The electronic device 1 of the present invention includes an upper control unit 2 as a master device, an I2C control unit 3 as a lower control unit connected to the upper control unit 2, an I2C bus 4 connected to the I2C control unit 3, and an I2C control unit. N slave devices 5-1 to 5-n connected to the bus 4, a stop condition generation circuit 6 connected to the I2C control unit 3,
N connected to this stop condition generation circuit 6
ACK monitoring unit 7, NACK monitoring unit 7 and host control unit 2
And a NACK notification circuit 8 connected between the two. Here, only the components that use the I2C bus are shown, and the components that are necessary for configuring the electronic device but are not involved in data transmission are not shown.

The electronic device 1 having the configuration shown in FIG. 1 is applied to, for example, a mobile phone. The upper control unit 2 is a CPU or ROM
It is configured using (Read Only Memory) and controls the entire mobile phone. The I2C control unit 3 controls the I2C bus 4 and the slave devices 5-1 to 5-n. In the slave devices 5-1 to 5-n, for example, 5-1 is an image sensor unit of a camera mounted on a mobile phone, and 5-n is a timer used to control a certain device. The stop condition generation circuit 6 uses the paragraph number [0005].
The stop condition signal described in 1 above is generated when the NACK is issued from the slave device, and is transmitted to the I2C bus 4 via the I2C control unit 3. In the NACK monitoring unit 7, the slave device (any one of 5-1 to 5-n) is N
It monitors whether or not it is in the ACK state. The NACK notification circuit 8
When the NACK monitoring unit 7 detects the NACK state, it notifies the upper control unit 2 of this. The higher-level control unit 2 that has received this notification notifies the slave devices (slave devices 5-1 to 5-5).
-Reset (reselect) one of the destinations in n.

FIG. 2 shows a bus control process in the electronic device of FIG. In the figure, "S" represents a step. In the following, it is assumed that the destination of the data (I2C data) from the host controller 2 is the slave device 5-1.
When the control of the I2C bus is started (S101), first,
I2C from the host controller 2 to the designated slave device 5-1
Transmission of I2C data is performed via the control unit 3 (S
102). In this transmission, the conventional one-time data is transmitted instead of repeating the data four times as in the conventional case.
If the transmission of the I2C data is completed without any problem and an ACK is returned from the slave device 5-1 to the I2C control unit 3 (S103), it is determined that the I2C data has been normally transmitted (S104), and the I2C data is normally transmitted. It ends (S105).

On the other hand, when the NACK of the slave device 5-1 is detected by the NACK monitoring unit 7 in S103, the stop condition generating circuit 6 automatically generates a stop condition signal based on this information (S106). Stop condition signal is I2
It is transmitted to the C control unit 3 and the slave device 5-1. With this stop condition signal, the I2C control unit 3 forcibly ends the transmission process, and the slave device 5
At -1, the receiving process is forced to end.

When the NACK monitoring section 7 detects a NACK, the NACK notifying circuit 8 causes the slave device 5-1.
Is sent to the upper control unit 2 (S1).
07). The upper control unit 2 receives the N from the NACK notification circuit 8.
When receiving the notification of ACK, the I2C control unit 3 is instructed to execute the process for retransmitting the I2C data to the slave device 5-1 (S108). When the communication procedure between the I2C control unit 3 and the slave device 5-1 is completed, the process is returned to S102, and the retransmission of the I2C data from the upper control unit 2 to the slave device 5-1 is started. Hereinafter, the above-described processing is repeatedly executed until it is normally transmitted.

As described above, the NACK monitoring unit 7 determines whether the data is transmitted once or not, and if it is in the NACK state, a stop condition signal is immediately generated to terminate the communication and the higher order. Since the NACK notification is sent to the control unit 2 to prepare for the start of the next transmission from the upper control unit 2, the NAC of the slave devices (5-1 to 5-n) conventionally performed by the upper control unit 2 is performed.
It is not necessary to monitor the K state, and the burden on the host controller 2 and the influence on the system are reduced. Further, it becomes possible to quickly perform data transmission or re-transmission to the slave devices 5-1 to 5-n. Further, since the data transmission at the time of ACK can be done once instead of the conventional four times, the data transmission time can be shortened.

FIG. 3 shows the configuration of the second embodiment of the electronic apparatus of the present invention. FIG. 4 shows a bus control method in the electronic device of FIG. The configuration of FIG. 3 differs from that of FIG. 1 in that a warning display unit 9 is connected to the NACK monitoring unit 7. This warning display unit 9 is used for the electronic device 1
The device or equipment to which is applied is a mobile communication device (mobile phone,
PHS (Personal Handyphone System) telephone etc.) and PD
If it is A (Personal Digital Assistant) or the like, it is possible to substitute the liquid crystal display or the incoming call LED (light emitting diode). Of course, a dedicated display and LE
D can also be provided.

In FIG. 4, the processing from S101 to S108 is the same as that in FIG. Therefore, the description is omitted here. When the preparation for transmitting the I2C data from the I2C control unit 3 to the slave device 5-1 is completed in S108, the warning display unit 9 operates (S201). When the NACK monitoring unit 7 detects that the NACK state is in the NACK state, the warning display unit 9 displays a warning on the warning display unit 9 based on the information. When a liquid crystal display or the like is used as the warning display unit 9, a warning is displayed by displaying a character message or a mark (illustration). If the warning display unit 9 is an LED or the like,
A warning can be issued by lighting or blinking this.

The user who sees the warning displayed on the warning display unit 9 can grasp the operation status of the device or equipment being used. In addition, if the warning display unit 9 operates many times or a state where the warning display unit 9 continues to operate occurs,
Since it is possible to warn that an abnormality has occurred in the electronic device, or a slave device has failed or damaged (for example, the camera unit has been damaged), it is possible to determine whether or not it is necessary to bring the device to the service station.

FIG. 5 shows the configuration of the second embodiment of the electronic apparatus of the present invention. The configuration of FIG. 5 differs from that of FIG. 1 in that the storage unit 1 is provided between the host control unit 2 and the I2C control unit 3.
0 is provided. In this storage unit 10,
Semiconductor memory is used in small devices, but hard disk in large systems.
Etc. can be used. The storage unit 10 stores the processing request information and the I information for the I2C control unit 3 by the upper control unit 2.
2C data is stored.

At the time of the first transmission, the processing request information and I2C data from the upper control unit 2 to the slave device 5-1 are stored in the storage unit 10. According to the processing request information, the I2C control unit 3 transmits the I2C data to the slave device 5-1 that is the transmission destination. After that, S1 in FIG. 2 or FIG.
The processing shown in 02 to S106 is executed. When the NACK state of the slave device 5-1 is determined in S103, the NACK notification from the NACK notification circuit 8 is sent to the storage unit 10 instead of the upper control unit 2. This NA
The processing request information is read from the storage unit 10 to the I2C control unit 3 based on the CK notification. Based on this processing request information, the I2C control unit 3 reads the I2C data to be transmitted from the storage unit 10, and the I2C control unit 3 retransmits the I2C data to the slave device 5-1. Like this
In the past, part of the work that was the role of the host controller 2
By substituting the control unit 3 and the storage unit 10 for the slave device, I2 can be transferred to the slave device without burdening the host control unit 2.
C data can be retransmitted. In addition, it is possible to prevent a decrease in the operating speed of the system.

[0026]

As is apparent from the above, according to the electronic device and the bus control method of the present invention, when data is transmitted from the host controller to the device, a stop condition signal is automatically generated in response to the NACK from the device. Then, the communication is terminated and the data is sent again from the host controller, so it is not necessary for the host controller to monitor the status of the device, which reduces the load on the host controller and affects the operating speed of the system. And the NACK state is released by the generation of the stop condition signal, so that the data can be retransmitted quickly.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a first embodiment of an electronic device of the present invention.

FIG. 2 is a flowchart showing a bus control process of the electronic device of FIG.

FIG. 3 is a block diagram showing a configuration of a second embodiment of an electronic device of the present invention.

4 is a flowchart showing a bus control process of the electronic device of FIG.

FIG. 5 is a block diagram showing a configuration of a third exemplary embodiment of an electronic device of the present invention.

[Explanation of symbols]

1 electronic equipment 2 Host controller 3 I2C controller 4 I2C bus 5-1 to 5-n slave devices 6 Stop condition generation circuit 7 NACK monitoring section 8 NACK notification circuit 9 Warning display 10 memory

Claims (9)

[Claims] 1. A high-order control unit that manages the whole and is a data transmission source, one or a plurality of devices that receive the data from the high-order control unit, and are connected to the one or a plurality of devices, respectively. I2
A C bus, a lower control unit that is connected to the I2C bus and controls the one or more devices under the control of the upper control unit, and the device that receives the data returns NACK, A stop condition generation circuit for generating a stop condition signal for forcibly ending the transmission process of the data based on NACK; and a device for controlling the upper control unit to monitor the occurrence of the NACK and to notify the upper control unit when the NACK is detected. NACK notifying that it is in NACK state and prompting retransmission of the data
An electronic device comprising a monitoring means. 2. The NACK monitoring means is for the NACK.
The electronic device according to claim 1, further comprising a warning display unit for warning that the user is in a state by displaying, blinking, or lighting a character message or mark. 3. The electronic device according to claim 1, wherein the upper control unit is connected to a storage unit that stores the processing request information provided to the lower control unit and the data. 4. The storage unit sends the stored processing request information and the stored data to the lower control unit when notified by the NACK monitoring means that the storage unit is in the NACK state. The electronic device according to claim 3. 5. The electronic device according to claim 1, wherein the upper control unit does not repeatedly transmit data having the same content in one transmission. 6. The electronic device according to claim 1, wherein the higher-order control unit functions as a master device, and the device is a peripheral circuit component that is subordinate to the higher-order control unit and functions as a slave device. . 7. The high-order control unit, the low-order control unit, the I2C bus, and the one or more devices are used in a mobile phone, another mobile communication device, or a mobile terminal device. Item 1. The electronic device according to item 1. 8. The upper control unit transmits data to a specified device via an I2C bus, and the device which receives the data returns ACK or NACK to the upper control unit according to a reception state, and the NACK is transmitted. In the bus control method of retransmitting the data from the upper control unit to the device in response to the above, a stop condition signal for forcibly ending the transmission process of the data in response to the occurrence of the NACK is generated, and A bus control method comprising transmitting the data to a device, and again transmitting the data from the upper control unit to the device based on the occurrence of the NACK. 9. The bus control method according to claim 8, wherein the step of retransmitting the data includes the step of warning the occurrence of the NACK.