Semiconductor device, radio communication terminal using the same, and inter-circuit communication system

Disclosed as one aspect is a semiconductor device including a transmission/reception interface that is used for transmission and reception of data, a processing unit that processes the data, a monitoring unit that monitors received data and detects a specific frame allowed to be transmitted regardless of a state of a circuit to transmit/receive the data, and a power management unit that controls power consumption of a circuit including the processing unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese patent application No. 2012-007733, filed on Jan. 18, 2012, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

The present invention relates to a semiconductor device, a radio communication terminal using the same, and an inter-circuit communication system.

In information equipment such as a radio communication terminal, one system is composed of a combination of semiconductor devices or circuits with different functions. Therefore, in order to reduce the power consumption of equipment, it is necessary to control the operating mode of each circuit in consideration of the status of communication performed between the circuits.

Japanese Unexamined Patent Application Publication No. 8-166838 discloses a technique related to a communication terminal, in which at the time of detecting a request for communication from the outside, a startup determination unit of a power control unit determines the validity of the communication based on a prestored communication ID or the like and turns on the power only when it is valid. Further, Japanese Unexamined Patent Application Publication No. 2011-519083 discloses a technique that, in a system including a host processor and a coprocessor, activates the host processor in accordance with an activation signal that is output from the coprocessor.

SUMMARY

The inventors of the present invention have found out various problems during development of a semiconductor device. According to embodiments disclosed in the present invention, a semiconductor device suitable for a radio communication terminal or the like, for example, is provided. More detailed features are made obvious by the following description of the invention and the accompanying drawings.

One aspect of the present invention includes a semiconductor device including a transmission/reception interface that is used for transmission and reception of data, a monitoring unit that monitors received data, and a power management unit that controls power consumption of a circuit.

According to the present invention, it is possible to provide a high-quality semiconductor device that is suitable for a radio communication terminal or the like, for example.

DETAILED DESCRIPTION

First Embodiment

Preferred embodiments of the present invention will be described in detail hereinafter with reference to the drawings. The present invention, however, is not limited to the below-described embodiments. The description hereinbelow is appropriately shortened and simplified to clarify the explanation.

<Overview of Radio Communication Terminal>

The overview of a radio communication terminal that is suitable for use as electronic equipment to which a semiconductor integrated circuit according to this embodiment is applied is described firstly with reference toFIGS. 1A and 1B.FIGS. 1A and 1Bare outline views showing configuration examples of a radio communication terminal500. Note thatFIGS. 1A and 1Bshow the case where the radio communication terminal500is a smartphone. However, the radio communication terminal500may be another radio communication terminal such as a feature phone (for example, a folding mobile phone terminal), a portable game terminal, a tablet PC (Personal Computer) or a notebook PC. Further, the semiconductor integrated circuit according to this embodiment is applicable also to equipment other than the radio communication terminal as a matter of course.

FIG. 1Ashows one principal surface (front surface) of a body501of the radio communication terminal500. On the front surface of the body501is a display device502, a touch panel503, several operating buttons504, and a camera device505. On the other hand,FIG. 1Bshows the other principal surface (back surface) of the body501. On the back surface of the body501is a camera device506.

The display device502is an LCD (Liquid Crystal Display), OLED (Organic Light-Emitting Diode) display or the like, and its display plane is mounted on the front surface of the body501. The touch panel503is mounted to cover the display plane of the display device502or mounted on the backside of the display device502to detect a user's contact position on the display plane. Specifically, a user can intuitively manipulates the radio communication terminal500by touching the display plane of the display device502with a finger or a special pen (which is typically referred to a stylus). Further, the operating buttons504are used for auxiliary manipulation on the radio communication terminal500. Note that such operating buttons are not mounted in some radio communication terminal.

The camera device506is a main camera that is mounted so that its lens unit is on the back surface of the body501. On the other hand, the camera device505is a sub-camera mounted so that its lens unit is on the front surface of the body501. Note that such a sub-camera is not mounted in some radio communication terminal.

Next, the configuration of a mobile communication terminal600to which a semiconductor device according to the present invention is applied is described with reference toFIG. 2.FIG. 2is a block diagram showing a configuration example of the mobile communication terminal600according to the first embodiment of the present invention. The mobile communication terminal600is incorporated into the radio communication terminal500shown inFIGS. 1A and 1B, for example. As shown inFIG. 2, the mobile communication terminal600includes an application processor601, a baseband processor602, an RF (Radio Frequency) subsystem603, a memory604, a battery605, a power management IC (PMIC: Power Management Integrated Circuit)606, a display unit607, a camera unit608, an operation input unit609, an audio IC610, a microphone611, and a speaker612.

The application processor601reads a program stored in the memory604and performs processing for implementing the functions of the mobile communication terminal600. For example, the application processor601runs an OS (Operating System) program from the memory604and further runs an application program that operates on the basis of the OS program.

The baseband processor602performs baseband processing including encoding (error correction coding such as convolutional coding or turbo coding) or decoding of data transmitted and received by the mobile communication terminal. To be more specific, the baseband processor602receives transmission data from the application processor601, encodes the received transmission data and transmits the data to the RF subsystem603. Further, the baseband processor602receives received data from the RF subsystem603, decodes the received data and transmits the data to the application processor601.

The RF subsystem603performs modulation or demodulation of data transmitted and received by the mobile communication terminal600. To be more specific, the RF subsystem603modulates the transmission data received from the baseband processor602by means of a carrier wave to generate a transmission signal and outputs the transmission signal through an antenna. Further, the RF subsystem603demodulates the received signal by means of a carrier wave to generate received data and transmits the received data to the baseband processor602.

The memory604stores a program and data used by the application processor601. Further, the memory604includes a nonvolatile memory in which stored data is maintained even when power is cut off and a volatile memory in which stored data is cleared when power is cut off.

The battery605is an electric battery and used in the case where the mobile communication terminal600operates not by external power. Note that the battery605may use the power of the battery605when an external power supply is connected as well. Further, it is preferred to use a secondary battery as the battery605.

The power management IC606generates internal power from the battery605or the external power. The internal power is supplied to each block of the mobile communication terminal600. At this time, the power management IC606controls the voltage of the internal power for each block to receive the internal power. The power management IC606makes voltage control of the internal power based on an instruction from the application processor601. Further, the power management IC606can control the supply and cutoff of the internal power for each block. Furthermore, when there is external power supply, the power management IC606makes charge control of the battery605as well.

The display unit607is a liquid crystal display device, for example, and displays various images in accordance with processing in the application processor601. The images displayed on the display unit607include a user interface image for a user to give an instruction for operation to the mobile communication terminal600, a camera image, a moving image and the like.

The camera unit608acquires an image in accordance with an instruction from the application processor601. The operation input unit609is a user interface to be operated by a user to give an instruction for operation to the mobile communication terminal600. The audio IC610decodes audio data transmitted from the application processor601and drives the speaker612and further encodes audio information obtained from the microphone611to generate audio data and outputs the audio data to the application processor601.

<Description of Configuration of Semiconductor Device According to First Embodiment>

A semiconductor device according to this embodiment is described hereinafter.FIG. 3is a block diagram showing an inter-circuit communication system including a semiconductor device10according to the first embodiment. InFIG. 3, a semiconductor device20that communicates with the semiconductor device10according to the first embodiment is also shown. The semiconductor device10corresponds to a first circuit, and the semiconductor device20corresponds to a second circuit. Further, the semiconductor device10is an application processor (in the following description and drawings, “APE” is used as the reference symbol of the application processor), for example. The semiconductor device20is a baseband processor (in the following description and drawings, “BB” is used as the reference symbol of the baseband processor), for example.

As shown inFIG. 3, the semiconductor device10includes a transmission/reception interface (for example, an interface unit11), a processing unit12, a power management unit14, and a monitoring unit15. Further, the semiconductor device10has a power control region13including circuits whose power consumption is controlled.

In the inter-circuit communication system according to the first embodiment, the case of performing communication in compliance with the HSI (High-speed Synchronous Serial Interface) specification defined in the MIPI (Mobile Industry Processor Interface) Alliance (which is referred to hereinafter as MIPI HSI) is described in the following example; however, the below-described technical idea is not limited to the HSI specification and is applicable to all communication methods to which the technical idea derived from the description is applied.

The interface unit11performs processing to transmit and receive data with an interface unit21. To be more specific, data to be transmitted is supplied from the processing unit12to the interface unit11, and the interface unit11transmits the supplied data to the semiconductor device20. Further, when the interface unit11receives data output from the semiconductor device20, the interface unit11supplies the data to the processing unit12.

Further, when transmitting data to the semiconductor device20, the interface unit11enables a wakeup signal AC_WAKE to wake up the semiconductor device20from the sleep mode. Further, the interface unit11outputs a transmission permission signal AC_READY indicating whether the device is ready to receive data to the semiconductor device20. The transmission permission signal AC_READY is in the enable state (for example, 1) when there is a free space in an input buffer of the interface unit11, and in the disable state (for example, 0) when there is some reason for not being able to receive data, such as when the interface unit11is in the low power consumption mode or when there is no free space in the input buffer.

Further, the interface unit11transmits one data using two signals: a data signal AC_DATA and a flag signal AC_FLAG. The flag signal AC_FLAG has a value to generate a clock signal as a result of the exclusive OR operation with the value of the data signal.

The processing unit12processes various data in the semiconductor device10. As one of data processing, when the interface unit11outputs a sleep permission notification in response to receiving a sleep permission frame that allows transition to the stop mode as data, the processing unit12according to the first embodiment outputs (enables) a power down control signal PD1in response to the sleep permission signal. Note that, when the transmission of data through the interface unit11is not completed, the processing unit12stops the output of the power down control signal PD1(for example, maintains the disable state).

The power management unit14controls whether the circuit included in a power control region13operates with first consumption power or operates with second consumption power which is lower than the first consumption power. Note that the power management unit14switches the consumption power of the circuit belonging to the power control region13by making control such as cutting off the power of the circuit belonging to the power control region13or changing or stopping a clock frequency to be supplied. In the following description, it is assumed that the power management unit14controls the consumption power by switching between the cutoff and supply of the power to the power control region13.

The operation of the power management unit14is described hereinafter in further detail. The power management unit14switches the consumption power of the processing unit12and the interface unit11from the first consumption power to the second consumption power upon output of the power down control signal PD1(for example, when it becomes enabled). Then, the power management unit14switches a circuit at least including the processing unit from a second operating mode where it operates with the second consumption power to a first operating mode where it operates with the first consumption power in response to a first return instruction signal RTN1. When switching the consumption power of the power control region13from the first consumption power to the second consumption power, the power management unit14enables a power control signal PC1, and, when switching it from the second consumption power to the first consumption power, the power management unit14disables a power control signal PC1

The monitoring unit15detects a specific frame that is allowed to be transmitted regardless of the state of a circuit to transmit/receive the data, and outputs the first return instruction signal RTN1to the power management unit14in accordance with the detected result. In the semiconductor device10according to the first embodiment, a break transmission command that is defined by the MIPI HSI is used as the specific frame. The monitoring unit15is described in detail later.

Further, in the block diagram ofFIG. 3, the semiconductor device20that communicates with the semiconductor device10is also shown. The semiconductor device20includes an interface unit21, a processing unit22, and a power management unit24. Further, the semiconductor device20has a power control region23where consumption power is controlled.

The interface unit21is a circuit having substantially the same configuration as the interface unit11, and it outputs a transmission permission signal CA_READY, a data signal CA_DATA and a flag signal CA_FLAG that correspond to the transmission permission signal AC_READY, the data signal AC_DATA and the flag signal AC_FLAG, respectively. Further, when the wakeup signal AC_WAKE that is output from the interface unit11is enabled, the interface unit21outputs a return instruction signal RTN2to the power management unit24. Note that the interface unit21does not output a wakeup signal CA_WAKE that corresponds to the wakeup signal AC_WAKE that is output from the interface unit11. This is because the semiconductor device10has a configuration that can return from the sleep mode without use of the wakeup signal. However, even if the interface unit21outputs the wakeup signal CA_WAKE, the interface unit11can just ignore it and thus no particular problem is caused in this embodiment.

The processing unit22processes various data in the semiconductor device20. As one of data processing, when the interface unit21outputs the sleep permission notification in response to receiving the sleep permission frame that allows transition to the stop mode as data, the processing unit22according to the first embodiment outputs (enables) a power down control signal PD2in response to the sleep permission signal. Note that, when the transmission of data through the interface unit21is not completed, the processing unit22stops the output of the power down control signal PD2(for example, maintains the disable state). Further, when a sleep return signal is supplied from the interface unit21, the processing unit22disables the power down control signal PD2.

The power management unit24controls whether the circuit included in the power control region23operates with first consumption power or operates with second consumption power which is lower than the first consumption power. Note that the power management unit24switches the consumption power of the circuit belonging to the power control region23by making control such as cutting off the power of the circuit belonging to the power control region23or changing or stopping a clock frequency to be supplied. In the following description, it is assumed that the power management unit24controls the consumption power by switching between the cutoff and supply of the power to the power control region23.

The operation of the power management unit24is described hereinafter in further detail. The power management unit24switches the consumption power of the processing unit22from the first consumption power to the second consumption power in response that the power down control signal PD2becomes enabled. Then, the power management unit24switches the consumption power of the power control region23from the second consumption power to the first consumption power in response that the power down control signal PD2becomes disabled or the return instruction signal RTN2is enabled. When switching the consumption power of the power control region23from the first consumption power to the second consumption power, the power management unit24enables a power control signal PC2, and, when switching it from the second consumption power to the first consumption power, the power management unit24disables a power control signal PC2.

<Detailed Description of Monitoring Unit>

The monitoring unit15is described hereinafter in detail.FIG. 4is a detailed block diagram of the monitoring unit15. As shown inFIG. 4, the monitoring unit15includes an ExOR circuit16, an inverter17, counters181and182, and a threshold determination circuit19.

The ExOR circuit16calculates the exclusive OR of the data signal CA_DATA and the flag signal CA_FLAG and generates a clock signal ExCLK. The inverter17inverts the clock signal ExCLK and generates a clock signal ExCLKb. The counter181counts up the count value if the data signal CA_DATA is Low level each time the rising edge of the clock signal ExCLK is input. The counter182counts up the count value if the data signal CA_DATA is Low level each time the rising edge of the clock signal ExCLKb is input. The threshold determination circuit19enables the return instruction signal RTN1(set it to High level, for example) in response that the total of the count value of the counter181and the count value of the counter182reaches a predetermined threshold.

Note that the counters181and182reset the count values when the return instruction signal RTN1becomes enabled or the High-level data signal CA_DATA is input.

In the above configuration, the monitoring unit15determines the period where the same value continues as the data signal CA_DATA based on the clock signal ExCLK and thereby detects the specific frame. The operation of the monitoring unit15shown inFIG. 4is described in detail.FIG. 5is a timing chart showing the operation of the monitoring unit15. As shown inFIG. 5, the data signal CA_DATA is data transmitted from the semiconductor device20to the semiconductor device10. The flag signal CA_FLAG is a signal having a value to generate a clock signal as a result of the exclusive OR operation with the data signal CA_DATA. Further, the simultaneous change in the logic level of the flag signal CA_FLAG and the data signal CA_DATA is inhibited.

Then, in the monitoring unit15, the ExOR circuit16generates the clock signal ExCLK based on the data signal CA_DATA and the flag signal CA_FLAG. Further, the inverter17generates the clock signal ExCLKb, which is an inverted signal of the clock signal ExCLK.

Then, when a break transmission command is transmitted as the data signal CA_DATA, Low level (for example, 0) continues for a longer period than the data length transmitted as the data signal CA_DATA. Therefore, in the case where a threshold that is preset for detecting the break transmission command is 33, for example, the monitoring unit15enables the return instruction signal RTN1(to 1, for example) at the point when Low level continues 33 times in sequence. Note that, although two bits of 0 are transmitted between the break transmission command and the data in the example ofFIG. 5, 0 between the break transmission command and the data is ignored in the receiving circuit (for example, the semiconductor device10).

Further, as shown inFIG. 5, when normal data is transmitted as the data signal CA_DATA, Low level does not continue 33 times in sequence. Therefore, the monitoring unit15does not enable the return instruction signal RTN1for the normal data. The normal data has a rule that the head of the data is always 1 and has a data length of 32 bits.

Note that the break transmission command is a signal to be used for correcting the lack of data synchronization when the synchronization of data is lost in the MIPI HSI, and it is a signal that is allowed to be transmitted even when the transmission permission signal CA_READY is disabled. In the semiconductor device10according to this embodiment, the case where the break transmission command is detected in the monitoring unit15and thereby enable the return instruction signal RTN1is described as an example. However, the signal detected by the monitoring unit15is not limited to the break transmission command but may be any signals received as the data signal CA_DATA as long as it is distinguishable from normal data and it is a command or the like that is designed to be used for another purpose.

<Description of Operation of Semiconductor Device According to First Embodiment>

The operation in the inter-circuit communication system shown inFIG. 3is described hereinafter.FIG. 6is a timing chart showing the operation of the inter-circuit communication system including the semiconductor device10according to the first embodiment.

In the example shown inFIG. 6, during the period before timing T1, data communication is performed between the semiconductor device10and the semiconductor device20. At this time, the semiconductor device20is in the normal operating mode where the wakeup signal AC_WAKE is enabled (for example, High level) and the transmission permission signal AC_READY is enabled (for example, High level), and the circuit belonging to the power control region23is in the operating mode. Further, the semiconductor device10is in the normal operating mode where the transmission permission signal CA_READY is enabled (for example, High level), and the circuit belonging to the power control region13is in the operating mode.

Then at timing T1, the semiconductor device10receives a sleep permission frame SLP as data D2. Consequently, in the semiconductor device10, the interface unit11outputs a sleep permission notification to the processing unit12; however, because the data transmission through the interface unit11is not completed, the processing unit12maintains the disable state of the power down control signal PD1.

Then, during the period from timing T1to timing T2, the semiconductor device10transmits the sleep permission frame SLP upon completion of the data transmission. At timing T2, the processing unit12of the semiconductor device10recognizes the completion of data transmission and, because the sleep permission notification is already received, enables the power down control signal PD1. Consequently, in the semiconductor device10, the power management unit14enables the power control signal PC1and cuts off the power to the power control region13. Then, the semiconductor device10transitions from the normal operating mode (the mode of operating with the first consumption power, for example) to the low power consumption mode (the mode of operating with the second consumption power, for example). At this time, the semiconductor device10disables the transmission permission signal CA_READY.

Further, at timing T2, the semiconductor device20receives a sleep permission frame from the semiconductor device10. Then, in the semiconductor device20, the interface unit21outputs a sleep permission notification to the processing unit22, and enables the power down control signal PD2. Consequently, in the semiconductor device20, the power management unit24enables the power control signal PC2and cuts off the power to the power control region23, and thereby the semiconductor device20transitions from the normal operating mode (the mode of operating with the first consumption power, for example) to the low power consumption mode (the mode of operating with the second consumption power, for example). At this time, the semiconductor device20disables the wakeup signal AC_WAKE and the transmission permission signal CA_READY.

Then, at timing T3, the semiconductor device20returns from the low power consumption mode upon receiving data from an RF subsystem, for example. At timing T4, the semiconductor device20transmits the break transmission command as a return request. At this time, the semiconductor device20enables the transmission permission signal CA_READY.

Further, at timing T4, in the semiconductor device10that has received the break transmission command, the monitoring unit15enables the return instruction signal RTN1, and the power management unit14disables the power control signal PC1. The semiconductor device10thereby transitions from the low power consumption mode to the normal mode.

Then, at timing T5, the semiconductor device10enables the wakeup signal AC_WAKE and the transmission permission signal AC_READY and starts data transmission. Further, at timing T5, the semiconductor device20starts data transmission in response that the transmission permission signal AC_READY becomes enabled.

Description of Comparative Example

A comparative example that has been studied by the present inventors is described hereinbelow.FIG. 7is a block diagram of an inter-circuit communication system according to the comparative example. The inter-circuit communication system according to the comparative example shown inFIG. 7includes a semiconductor device10ain place of the semiconductor device10. The semiconductor device10aincludes an interface unit11a, a processing unit12a, and a power management unit14a. Further, the semiconductor device10ahas a power control region13awhere power consumption is controlled.

The interface unit11ais a circuit block that corresponds to the interface unit21, the processing unit12aimplements the functions of the semiconductor device10a, and the power management unit14ais a circuit block that corresponds to the power management unit24. Further, the power control region13aincludes the processing unit12aand does not include the interface unit11a. This is because the semiconductor device10starts the receiving operation based on the wakeup signal CA_WAKE that is output from the semiconductor device20and thus the interface unit11acannot enter the sleep mode.

Note that the processing unit12aenables a power down control signal PD1abased on an instruction from the interface unit11a, and the power management unit14aenables a power control signal PC1ain response that the power down control signal PD1abecomes enabled. Further, the interface unit11aenables a return instruction signal RTN1ain response that the wakeup signal CA_WAKE becomes enabled. Further, the power management unit14adisables the power control signal PC1ain response that the return instruction signal RTN1abecomes enabled.

In the inter-circuit communication system according to this comparative example, the processing unit12aof the semiconductor device10acan transition to the sleep mode at the end of communication; however, because it needs to wait for the wakeup signal CA_WAKE from the semiconductor device20to return to the normal mode from the sleep mode, the interface unit11acannot transition to the sleep mode. Further, in the inter-circuit communication system according to this comparative example, it is necessary to include a terminal and a signal path for transmitting the wakeup signal CA_WAKE that is used for return processing, which causes an increase in the number of terminals and the substrate area required for implementation.

<Advantage of Semiconductor Device According to First Embodiment>

As described above, the semiconductor device10according to the first embodiment includes the monitoring unit15and the power management unit14that controls the operating mode of the power control region13based on the return instruction signal RTN1that is output from the monitoring unit15. When the return instruction signal RTN1becomes enabled, the power management unit14switches the power control region13from the mode of operating with the second consumption power to the mode of operating with the first consumption power which is higher than the second consumption power.

Accordingly, the semiconductor device10can return from the low power consumption mode without receiving the wakeup signal CA_WAKE from the semiconductor device20. Thus, with use of the semiconductor device10, the semiconductor device10can reduce the number of signals that are used for the transition to and return from the low power consumption mode.

Further, in the semiconductor device10, there is no need to keep the interface unit11in the operating mode in order to monitor the state of the wakeup signal CA_WAKE that is used for the return. Therefore, the semiconductor device10can reduce the power consumption of the interface unit11during the period of operating with the second consumption power with the lower power consumption.

Further, in the semiconductor device10, the break transmission command that is used for another purpose in terms of specification is used as the signal to be used to cause the operating mode to return to the normal operating mode. Therefore, with use of the semiconductor device10, there is no need to prepare a command to be used to allow the operating mode to return. It is thereby possible to maintain compatibility with the semiconductor device capable of operating in compliance with the specification.

Further, although, in the semiconductor device10, the monitoring unit15is used for detecting the break transmission command, the monitoring unit15can be composed of a very simple circuit as shown inFIG. 4. Thus, the semiconductor device10can avoid a significant increase in circuit scale with the addition of the monitoring unit15. Further, because the monitoring unit15operates based on the clock signal ExCLK that is generated on the basis of the data signal CA_DATA and the flag signal CA_FLAG, the clock signal ExCLK is not generated during the period with no data transmission and reception, thus not consuming power. Because the power consumption in the monitoring unit15is only during the period with data transmission and reception, the semiconductor device10can further reduce the power consumption in the low power consumption mode.

Second Embodiment

Description of Configuration of Semiconductor Device According to Second Embodiment

FIG. 8is a block diagram showing an inter-circuit communication system including a semiconductor device according to the second embodiment. As shown inFIG. 8, in the inter-circuit communication system according to the second embodiment, each of two semiconductor devices that communicate with each other includes a monitoring unit that monitors a specific frame (for example, break transmission).

In the example shown inFIG. 8, the inter-circuit communication system according to the second embodiment includes a semiconductor device30in place of the semiconductor device20shown inFIG. 3. The semiconductor device30includes an interface unit31, a processing unit32, a power management unit34, and a monitoring unit35. Further, the semiconductor device30has a power control region33that includes the interface unit31and the processing unit32.

The interface unit31corresponds to the interface unit11, the processing unit32corresponds to the processing unit12, the power management unit34corresponds to the power management unit14, and the monitoring unit35corresponds to the monitoring unit15, and therefore the detailed description of each unit is omitted. Note that the power management unit34enables a power control signal PC3in response that a power down control signal PD3that is output from the processing unit32becomes enabled, thereby cutting off the power of the circuit belonging to the power control region33. Further, the power management unit34disables the power control signal PC3in response that a return instruction signal RTN3that is output from the monitoring unit35becomes enabled, thereby allowing the power of the power control region33to return.

<Description of Operation of Semiconductor Device According to Second Embodiment>

In the inter-circuit communication system according to the second embodiment, each of the semiconductor devices that communicate with each other includes the monitoring unit and thereby perform processing to allow the power of the power control region to return without use of the wakeup signal AC_WAKE and the wakeup signal CA_WAKE.FIG. 9is a timing chart showing the operation of the inter-circuit communication system according to the second embodiment.

The timing chart ofFIG. 9shows the case where the same operation as the operation of the inter-circuit communication system according to the first embodiment shown inFIG. 6is performed using the inter-circuit communication system according to the second embodiment. As show inFIG. 9, in the inter-circuit communication system according to the second embodiment, the semiconductor device10and the semiconductor device30communicate with each other without use of the wakeup signal AC_WAKE. Note that, although not shown inFIG. 9, when a break transmission command is transmitted from the semiconductor device10to the semiconductor device30, the monitoring unit35detects the break transmission command and enables the return instruction signal RTN3. In response that the return instruction signal RTN3becomes enabled, the power management unit34disables the power control signal PC3, thereby allowing the power of the power control region33to return.

<Advantage of Semiconductor Device According to Second Embodiment>

As described above, with use of the inter-circuit communication system according to the second embodiment, the semiconductor device30can return from the low power consumption mode without use of the wakeup signal AC_WAKE. Thus, the inter-circuit communication system according to the second embodiment can perform the same operation as the inter-circuit communication system according to the first embodiment, reducing the number of lines between the semiconductor device10and the semiconductor device30.

Third Embodiment

Description of Configuration of Semiconductor Device According to Third Embodiment

FIG. 10is a block diagram showing an inter-circuit communication system including a semiconductor device40according to the third embodiment. As shown inFIG. 10, the inter-circuit communication system according to the third embodiment includes the first circuit (for example, the semiconductor device40) that communicates with the second circuit (for example, the semiconductor device20) described in the first embodiment. The semiconductor device40is a semiconductor device capable of selecting a circuit block to be returned in accordance with a received signal or command. Thus, the inter-circuit communication system according to the third embodiment includes the semiconductor device20according to the first embodiment and the semiconductor device40having a new function, and therefore the semiconductor device40is particularly described hereinbelow.

The semiconductor device40includes an interface unit41, a first processing unit421, a second processing unit422, a power management unit44, and a monitoring unit45. Further, the semiconductor device40has a power control region431including the first processing unit421as a first power control region, and has a power control region432including the second processing unit422as a second power control region.

The interface unit41is a communication interface for transmitting and receiving data. To be more specific, the interface unit41transmits data signal AC_DATA and flag signal AC_FLAG as transmission data, and receives data signal CA_DATA and flag signal CA_FLAG as received data. Then, the interface unit41supplies the received data to the first processing unit421or the second processing unit422. Further, the interface unit41generates the transmission data based on data supplied from the first processing unit421or the second processing unit422.

Further, the interface unit41enables the transmission permission signal AC_READY when it is ready to receive data. The interface unit41transmits the transmission data during the period when the transmission permission signal CA_READY that is output from the semiconductor device20is enabled.

Further, when it becomes necessary to transmit data to the semiconductor device20, the interface unit41enables the wakeup signal AC_WAKE. Furthermore, when the wakeup signal CA_WAKE that is output from the semiconductor device20is enabled, the interface unit41enables a second return instruction signal RTN41and, when the wakeup signal CA_WAKE is disabled, the interface unit41disables the second return instruction signal RTN41.

The first processing unit421includes a CPU, for example, and implements some of the functions of the semiconductor device40. The second processing unit422includes a DSP (Digital Signal Processor), for example, and implements some of the functions of the semiconductor device40. It is assumed that the power consumption during operation of the second processing unit422is lower than that of the first processing unit421.

Further, as one of data processing, when the interface unit41outputs a sleep permission notification in response to receiving a sleep permission frame that allows transition to the stop mode as data, the first processing unit421outputs a power down control signal PD41in response to the sleep permission signal. Note that, when the transmission of data through the interface unit41is not completed, the first processing unit421stops the output of the power down control signal PD41.

Further, as one of data processing, when the interface unit41outputs a sleep permission notification in response to receiving a sleep permission frame that allows transition to the stop mode as data, the second processing unit422outputs a power down control signal PD42in response to the sleep permission signal. Note that, when the transmission of data through the interface unit41is not completed, the second processing unit422stops the output of the power down control signal PD42.

The power management unit44includes a first power management unit441and a second power management unit442. The first power management unit441controls whether the circuit included in the power control region431operates with first consumption power or operates with second consumption power which is lower than the first consumption power. The second processing unit422controls whether the circuit included in the power control region432operates with the first consumption power or operates with the second consumption power which is lower than the first consumption power. Note that the power management unit441,442switches the consumption power of the circuit belonging to the power control region431,432by making control such as cutting off the power of the circuit belonging to the power control region431,432or changing or stopping a clock frequency to be supplied. In the following description, it is assumed that the power management unit441,442controls the consumption power by switching between the cutoff and supply of the power to the power control region431,432.

The operation of the power management unit44is described hereinafter in further detail. The power management unit441switches the consumption power of the first processing unit421from the first consumption power to the second consumption power upon output of the power down control signal PD41(for example, when it becomes enabled). Further, the power management unit442switches the consumption power of the second processing unit422from the first consumption power to the second consumption power upon output of the power down control signal PD42(for example, when it becomes enabled). Then, the power management unit441switches the circuit at least including the first processing unit421from the second operating mode where it operates with the second consumption power to the first operating mode where it operates with the first consumption power in response to a second return instruction signal RTN41. Further, the power management unit442switches the circuit at least including the second processing unit422from the second operating mode where it operates with the second consumption power to the first operating mode where it operates with the first consumption power in response to a first return instruction signal RTN42.

When switching the consumption power of the power control region431from the first consumption power to the second consumption power, the power management unit441enables a power control signal PC41, and when switching it from the second consumption power to the first consumption power, the power management unit441disables the power control signal PC41. Further, when switching the consumption power of the power control region432from the first consumption power to the second consumption power, the power management unit442enables a power control signal PC42, and when switching it from the second consumption power to the first consumption power, the power management unit442disables the power control signal PC42.

The monitoring unit45is the same circuit as the monitoring unit15according to the first embodiment. However, in the semiconductor device40, because the interface unit41also generates the return instruction signal, the return instruction signal RTN42that is generated by the monitoring unit45is referred to hereinafter as the first return instruction signal RTN42for differentiation.

<Description of Operation of Semiconductor Device According to Third Embodiment>

The operation in the inter-circuit communication system that includes the semiconductor device40according to the third embodiment is described hereinafter.FIGS. 11 and 12are timing charts showing the operation of the inter-circuit communication system including the semiconductor device40according to the third embodiment. Note that the timing chart ofFIG. 11shows the case of performing the operation that allows only the second processing unit422including a DSP to return as return processing. The timing chart ofFIG. 12shows the case of performing the operation that allows only the first processing unit421including a CPU to return as return processing.

As shown inFIG. 11, the process to transition to the low power consumption mode (process of timing T21to T23) in the inter-circuit communication system according to the third embodiment is the same as the process in the inter-circuit communication system according to the first embodiment. Note that, in the semiconductor device40according to the third embodiment, upon receiving the sleep permission frame SLP, the sleep permission notification is given to the first processing unit421and the second processing unit422, allowing the two processing units to enter the low power consumption mode.

Then, at timing T23, when the semiconductor device20returns from the low power consumption mode upon receiving data from an RF subsystem, for example. At timing T24, the semiconductor device20transmits the break transmission command as a return request. At this time, the semiconductor device20enables the transmission permission signal CA_READY.

Further, at timing T24, in the semiconductor device40that has received the break transmission command, the monitoring unit45enables the first return instruction signal RTN42, and the power management unit44disables the power control signal PC42. The semiconductor device40thereby allows only the second processing unit422including the DSP to transition from the low power consumption mode to the normal mode.

Then, at timing T25, the semiconductor device40enables the wakeup signal AC_WAKE to transmit data supplied from the second processing unit422and also enables the transmission permission signal AC_READY. The semiconductor device40thereby starts data transmission. Further, at timing T25, the semiconductor device20starts data transmission in response that the transmission permission signal AC_READY becomes enabled.

In the timing chart shown inFIG. 12also, the process to transition to the low power consumption mode (process of timing T31to T33) in the inter-circuit communication system according to the third embodiment is the same as the process in the inter-circuit communication system according to the first embodiment.

Then, at timing T33, when the semiconductor device20returns from the low power consumption mode upon receiving data from an RF subsystem, for example. At timing T34, the semiconductor device20enables the wakeup signal CA_WAKE as a return request. At this time, the semiconductor device20enables the transmission permission signal CA_READY.

Further, at timing T34, the interface unit41in the semiconductor device40enables the second return instruction signal RTN41in response that the wakeup signal CA_WAKE becomes enabled, and the power management unit44disables the power control signal PC41. The semiconductor device40thereby allows only the first processing unit421including the CPU to transition from the low power consumption mode to the normal mode.

Then, at timing T35, the semiconductor device40enables the wakeup signal AC_WAKE to transmit data supplied from the first processing unit421and also enables the transmission permission signal AC_READY. The semiconductor device40thereby starts data transmission. Further, at timing T35, the semiconductor device20starts data transmission in response that the transmission permission signal AC_READY becomes enabled.

<Advantage of Semiconductor Device According to Third Embodiment>

As described above, the semiconductor device40according to the third embodiment can select the way power returns in accordance with the type of the signal transmitted from the semiconductor device20. The wakeup signal CA_WAKE that is transmitted from the semiconductor device20is a signal defined by the MIPI HSI specification or the like. Thus, the semiconductor device40according to the third embodiment can have a larger number of return modes than the number of return modes conceivable from the specification by using a signal defined by the specification. Further, with use of the semiconductor device40, the number of signal lines does not increase with an increase in the number of return modes. Thus, by using the semiconductor device40according to the third embodiment, it is possible to increase the number of return modes without increasing the number of signal lines.

Further, the semiconductor device40according to the third embodiment can select a circuit block to be returned in accordance with the return mode. Thus, the semiconductor device40according to the third embodiment allows only a circuit block required for processing to return and an unnecessary circuit block to remain in the low power consumption mode. By such control, the semiconductor device40according to the third embodiment can reduce the wasteful power consumption.

The first to third embodiments can be combined as desirable by one of ordinary skill in the art.

For example, the circuit of the monitoring unit shown inFIG. 4is just an example and may be altered as appropriate in accordance with a command to be detected.