KR100446568B1 - Communication control method and electronic device - Google Patents

Abstract

When the controller controls the target, useless communication is removed and at the same time easier control is achieved. When the personal computer sends a command to the VTR requesting REWIND execution, the VTR sends a response indicating OK to the request and simultaneously starts the REWIND in the internal recording / reproducing system. When the mechamode changes from REWING to STOP, the VRT generates an event and reports the change to the personal computer. Upon receiving this event, the personal computer immediately sends a command to the VTR requesting that the mecha mode be set to PLAY. Upon receiving this command, the VTR sends a response indicating OK to this command and also sets the mode of the recording / reproducing system to PLAY.

Description

Communication control method and electronic device

The present invention relates to a plurality of interconnected by a communication control bus for transmitting control signals and information signals included in a bus such as, for example, a serial bus according to IEEE-1394 (hereinafter referred to as an IEEE 1394 serial bus). TECHNICAL FIELD The present invention relates to a system for communicating between electronic devices, and more particularly, to a communication control method and an electronic device that eliminates communication that is not useful and makes the control easier when the electronic device controls the operation of another electronic device.

Consider a system in which a plurality of electronic devices are interconnected via a communication control bus such as an IEEE-1394 serial bus that transmits control signals and information signals, and information signals and control signals are communicated between these electronic devices.

9 shows an example of such a system. The system includes a hard disk unit 1, a personal computer 2, a television receiver (hereinafter referred to as TV) 3, a video tape recorder (hereinafter referred to as VTR) 4 and a set top box. box) 5. In addition, the hard disk unit 1 and the personal computer 2 and the VTR 4, the VTR 4 and the TV 3, and the VTR 4 and the set top box 5 are connected to the IEEE 1394 serial buses 6 to 6; 9) are interconnected by each. Here, #A to #E denote each node IDs on the system composed of the hard disk unit 1, the personal computer 2, the TV 3, the VTR 4, and the set top box 5. As shown in FIG.

Signal transmission at each electronic device (hereinafter referred to as a device) in the system is performed by time division multiplexing every predetermined communication cycle (e.g., 125 Hz) as shown in FIG. Signal transmission begins when an electronic device called a cycle master sends out a cycle start packet on the bus indicating the start time of a communication cycle.

In one communication cycle, the communication type includes two types, that is, an ISO communication type (hereinafter, “isochronous” is referred to as “Iso”) and a control command that simultaneously transmit information signals such as video data and audio data. Async communication type (hereinafter, "asynchronous" is referred to as "Async") that transmits the same control signal asynchronously. In addition, the Iso communication packet is transmitted before the Async communication packet. By assigning channel numbers 1, 2, 3, ..., n to each Iso communication packet, a plurality of data can be distinguished. Before the transmission of the Iso communication packet is completed, the period until the next cycle start packet is used to transmit the Async communication packet.

In Async communication, when an electronic device requests something for another electronic device, the electronic device used by this arbitrary device is called a command, and the side of transmitting this command included in a packet is called a controller. In addition, the side which receives this instruction is called a target. This target sends back a packet with a control signal representing the result of the execution of the command (called a response) to the controller each time it is requested.

These commands and responses are communicated between one controller and one target and are initiated by sending a command and completed by sending back a response called command processing. The target must return a response as soon as possible (eg, within 100 ms) after the command is received. This is because the controller side can keep waiting for a long time and processing can be delayed when processing is delayed and no response is returned due to some failure.

The controller can perform a specific action on the target or query the current target state. Any electronic device in the system can start and end command processing. In other words, any device can act as a controller or target.

11 illustrates a configuration of an Async communication packet including a control signal. Commands and responses have the same configuration. In FIG. 11, data of a packet is sequentially transmitted from top to bottom and from left to right.

A packet consists of a packet header and a data block. In addition, the standard of all the packet header and data CRC in the data block, i.e., halftone, is determined by IEEE 1394 and the contents of the data block are destined for the destination from the electronic device shown as the source ID of the packet header. ) Is recorded at an address shown in a destination offset of the electronic device shown by ID.

For example, in FIG. 9, when a command is sent from the personal computer 2 to the VTR 4, each of the source ID, destination ID, and destination offset stores the command at #B, #D, and VTR 4; Memory space allocated as an area. When the personal computer 2 sends the command to all the electronic devices in the system, the 16 bits of the destination ID are set to "all one". This type of communication is called broadcast.

In the data block shown in FIG. 11, a command transaction set (CTS) shows a command type. In addition, CT / RC (command type / reponse code) shows the request type in the case of a command and the response type for the request in the case of a response. The header address (HA) indicates whether the other party making the request is the entire device or a subdevice (functional unit) in the device as in the case of a command and the HA indicates that the other party is in the case of a response. Recognizing that it responds is the same as the command. The operation code (OPC) shows the command code, that is, the concrete demand and the parameters required for this request are shown with the OPR (operand) following the OPC.

Fig. 12 shows, by way of example, the structure of a portion of the devices in the system that take a VTR and exchange the commands and responses described above. This VTR has a VTR device 11 and an IEEE 1394 bus transmit-receive block 12.

The VTR device 11 is made up of a microcomputer and processes commands related to a tuner (not shown) in the VTR and a VTR subdevice 13 for processing commands related to a recording / reproducing system (not shown) in the VTR. And a tuner subdevice 14 for processing and a timer subdevice 15 for processing an instruction or the like related to a timer (not shown) in the VTR. These subdevices are formed by the software of the microcomputer.

The IEEE 1394 bus transmit-receive block detects an Async communication packet received over the bus and sends a command in this packet to the VTR device 11. The VTR device 11 operates the subdevices 13 to 15 in accordance with the specific request of the command when the command is received. For example, when a fast feed (FF) command addressed to the VTR subdevice 13 is received, the command is passed to the VTR subdevice 13. The VTR subdevice 13 executes processing for controlling the mechanical system of the recording / reproducing system in the VTR to perform FF. In addition, the VTR subdevice 13 monitors the mechanical modes, time codes, and the like of various states of the recording / reproducing system to generate a response when a request is made. This response is sent by the VTR device 11 to the IEEE 1394 bus transmit-receive block 12. The IEEE 1394 bus transmit-receive block 12 sends a response to the bus contained in the Async communication packet.

FIG. 13 shows the format structure of a command and a response targeting a VTR and a sample structure of the command and a response. As shown in Fig. 13, "0" is used as the CTS. For example, a command for requesting slow playback for the VTR subdevice 13 in the VTR shown in FIG. 12 is shown in FIG. 13C. In addition, the command to query the VTR subdevice 13 for the hour-minute-second-frame of the current value of the time code is shown in FIG. 13 (e) and the response returned for the command is FIG. 13 (f). Is shown.

FIG. 14 shows an example of a device in which the personal computer 2 acts as a controller in the system shown in FIG. 9 to query the status of all other devices in the system and display this status on its display unit. 14 will now be described later.

First, when the personal computer sends a command to the TV inquiring about the input mode to the TV, the response 'VTR' is returned from the TV. Next, when sending a command to the VTR to query the VTR about the mechamode of the VTR subdevice, the response 'STOP' is returned. Then, when a command to inquire about the time code of the VTR subdevice is transmitted, a response of "0 hour 25 minutes 49 seconds 24 frames" is returned. In addition, when a command to query the set top box about the receive channel is sent to the set top box, the response 'CH6' is returned.

When the command is sent in a similar manner and finds that the mode, the time code of the VTR subdevice and the receiving channel of the set top box are changed, the display on the display unit is changed at this time point.

Fig. 15 shows an apparatus in which a personal computer inquires about the state of the VTR and transmits the next command, which "rewinds to the head of the tape and plays it again." This will be described with reference to Fig. 15 below. Will be.

First, when a personal computer executes REWIND by sending a command requesting a VTR, the VTR returns a response notifying OK for this request and starts the REWIND in the recording / reproducing system at the same time.

The personal computer sends a command to inquire about the time code or a question to mecha mode even after receiving a response of OK from the VTR to REWIND. The personal computer then informs in advance of the time that the REWIND has been completed, then inquires again about the time code and sends a command to set the mecha mode after the timing has been reached, returning a response indicating that this mecha mode is 'STOP'. Play after it is done. The VTR returns a response notifying OK to this request upon receiving the command and also starts playing in the recording / reproducing system.

In the devices shown in Figures 14 and 15, these devices are structured such that the target returns a response only when the controller sends a command. Therefore, when the controller frequently sends a command to confirm that the target is in a predetermined state, it monitors the response of this command.

Therefore, when the state of the apparatus in the system is always displayed as in the example shown in FIG. 14 and when a series of operations are sequentially controlled in a predetermined order as shown in FIG. And control from the controller becomes difficult. In such an apparatus, the timing of displaying a situation change or the timing of performing the next control of a series of operations is delayed.

SUMMARY OF THE INVENTION The present invention provides a communication control method and an electronic device that eliminates communication that is not useful in view of such a problem and makes the control easier when the controller controls the target.

In order to solve the above-mentioned problem, a communication control method according to the present invention is connected to each other by communication control buses, in which a plurality of electronic devices can include control signals and information signals together, and the information signals and the In a system in which control signals are communicated between the electronic devices, when the electronic devices control the operation of other electronic devices using the control signal, the other electronic device uses the control signal to determine a predetermined state therein. It is characterized by reporting a change.

The other electronic device (target) receives a control signal for starting and stopping a report from the electronic device (controller) on the control side and starts or stops the report according to the control signal. The reporting of the internal state change may be made only for the electronic device on the control side or for all the electronic devices in the system. The destination of this report can be specified by the electronic device on the control side. Moreover, it is also possible to configure such that one kind of change in the designated internal state is immediately reported from the electronic device on the control side.

In addition, the electronic device according to the present invention is connected to each other by communication control buses in which a plurality of electronic devices may include control signals and information signals together, wherein the information signals and control signals are between the electronic devices. A first means for detecting a predetermined state change inside the apparatus, and a second means for sending a state change detected by the first means to the communication control bus by the control signal. It includes an electronic device.

In the electronic device according to the present invention, a plurality of means for detecting a predetermined state change in the device and a third means for performing centralized control of the state change detected by the plurality of means are further provided. It may be.

According to the present invention, the electronic device on the control side sends a request to report a change in a predetermined internal state or a request to stop reporting to the electronic device on the control side. The electronic device on the control side reports a state change by using a control signal when a predetermined state change occurs inside. In the electronic device on the control side, the first means detects the state change and the second means transmits the state change to the communication control bus by a control signal.

As described in detail above, according to the present invention, the effects described in the following items (1) to (5) are obtained.

(1) Since the device on the control side (target) reports immediately at the time when a predetermined state change occurs, the device on the control side (controller) frequently sends a command to monitor the state of the device on the control side. You don't need a long time to take. Therefore, when an application in which a series of operations are to be controlled in order is performed, control from the apparatus on the control side becomes easier, and unnecessary communication is not performed for a long time.

(2) Since the start or stop of the report can be controlled by the device on the control side by sending a control signal requesting the start and stop of the report to the device on the control side, the report can be received only when necessary. It is also possible that only certain devices, not all devices in the system, are arranged to receive the report. As a result, when multiple devices are present in the system, it is possible to avoid congestion of the communication control bus.

(3) Control from the apparatus on the control side is made easier by providing a central control means for the detection of a change of state in the apparatus.

(4) The communication control becomes simpler, and the state change report is configured to report only one type of the state change designated once by the control side device without real change of the conventional command processing. Can be.

(5) An application which requires the next operation by using the fact that an application which displays immediately when reporting a change of state or another device on the other side has become a predetermined state is feasible.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. This embodiment is based on the prior art shown in FIGS. 8 and 12.

Figure 1 shows an example of commands and responses used in one embodiment of the present invention.

In FIG. 1A, a command for requesting to report an event to the VTR is shown. Specifically, the request is made to report a change in the mechacode and timecode by generating an event to a controller in the VTR subdevice.

Referring to Fig. 12, the processing when the VTR receives the command will be described. The IEEE 1394 bus transmission / reception block 12 in the VTR transmits an Async communication packet command received via the bus. Since the HA of the command is a VTR subdevice 13, the VTR device 11 transmits a command to the VTR subdevice 13.

Fig. 1 (b) shows the response of the command shown in Fig. 1 (a) to return to the controller by the VTR upon receipt. Specifically, it is understood that an event is reported to the controller when the mecha mode and timecode are generated by the VTR subdevice.

1 (c) shows an example of a timecode event generated by the VTR subdevice. Referring to Fig. 12 for the process by which the VTR reports this timecode event, the VTR subdevice 13 monitors the timecode of the recording / reproducing system and generates a timecode event when a timecode of 1 second, for example, occurs. do. The VTR device 11 immediately sends the timecode event to the IEEE 1394 bus transmit / receive block 12. This IEEE 1394 bus transmit / receive block 12 transmits this timecode event contained in the Async communication packet.

FIG. 1 (d) shows a command for requesting the TV to stop reporting on an event relating to the input mode, and FIG. 1 (e) shows an OK response to the command.

FIG. 1 (f) shows a command to request the set-top box to report when an event occurs and the receiving channel is changed. In addition, this command requires the event to be sent, in short, to report the event to all other devices in the system.

Fig. 1 (g) shows the response to return to the controller by the set top box when the command shown in Fig. 1 (f) is received. Figure 1 (h) shows an example of a receive channel event generated by the set top box, which occurs when the tuner's reception is changed to channel 6. When this received channel event is reported to all devices, the destination ID of the header of the Async communication packet is set to 'All 1'.

In this way, ON / OFF of events are distinguished from each other by an operation code. In addition, it is distinguished whether the other party who receives the event by the operator is limited to the controller or all devices in the system.

2 shows an application in which the personal computer 2 acts as a controller and displays on the display unit using instructions which cause the state of all other devices in the system to generate the events shown in FIGS. 1 and 2. have.

First, although not shown, the personal computer and the VTR exchange commands for the responses shown in Figs. 1 (a) and 1 (b), and the personal computer and the TV are shown in Figs. 1 (d) and 1 (e). The personal computer and the set top box exchange commands for the response shown in FIGS. 1 (f) and 1 (g). In addition, the VTR is commanded to generate an event when the mega mode of the VTR is changed and when the time code is changed (by 1 second during REC and PLAY and 1 minute during FF and REWIND) and also serves as a controller. Are instructed to report to the personal computer.

As shown in Fig. 2, when the mecha mode is changed from 'STOP' to 'PLAY', the VTR immediately generates an event indicating that the mecha mode is PLAY and transmits this event to the personal computer. Referring to FIG. 12, when the user manipulates the VTR such that the operation mode of the recording / playback system is changed from 'STOP' to 'PLAY', the VTR sub device 13 indicates that the mecha mode is 'PLAY'. Happens immediately. This event is sent from the VTR device 11 to the IEEE 1394 bus transmit / receive block 12 and via the bus to a personal computer.

Upon receiving the event, the personal computer changes the mecha mode of the VTR displayed on the display unit from 'STOP' to 'PLAY'.

In addition, when the receiving channel changes from 'CH5' to 'CH6', the set top box generates an event indicating that the receiving channel is 'CH6' and transmits this event to the personal computer. This personal computer immediately changes the reception channel displayed on the display unit from 'CH5' to 'CH6' upon reception of this event.

The VTR also generates an event representing the hour-minute-second-frame of the time code and sends it to the personal computer whenever the time code changes by one minute. Upon receiving this event, the personal computer updates the time code displayed on the display unit.

In this method, the controller is sufficient to wait for a report on the event received from the target after the command to turn the event is changed for a response according to an embodiment of the present invention. Therefore, the traffic is significantly reduced compared to the example shown in FIG. 14, and the state change can be displayed immediately.

FIG. 3 shows an application example for "rewinding and playing back to tape head" using the command to turn the event shown in FIG. Similar to FIG. 2, the exchange of commands to turn the event on for a response is completed between the personal computer and the other device and the VTR is also changed in time mode ('REC' and 'PLAY) when there is a change in the mecha mode of the VTR subdevice. 'In seconds is also commanded to trigger an event when there is a change (in minutes during' FF 'and' REWIND ') and sends it to the controller personal computer.

In Fig. 3, when the personal computer sends a command to the VTR to execute REWIND, the VTR sends a response indicating OK for the request and also starts the REWIND in the recording / reproducing system.

The VTR generates an event during REWIND and sends it to the personal computer whenever the time code changes in minutes. Also, an event is generated when the mecha mode changes from 'REWIND' to 'STOP' and it is sent to the personal computer.

When an event is received indicating that the mecha mode has changed from VTR to 'STOP', the personal computer immediately sends a command to set the command to 'PLAY' in the mecha mode. Upon receiving this command, the VTR sends a response indicating OK to that command and sets the mode of the recording / playback system to 'PLAY'.

In this method, according to the present invention, the personal computer waits for an event indicating that the mecha mode is changed to 'STOP' and immediately sends a 'PLAY' command upon receiving the event. Therefore, the traffic is significantly reduced than the conventional example shown in Fig. 15, and can immediately send the next command when a state change occurs.

FIG. 4 shows an example in which an event is changed and a command shown in FIG. 1 requesting a broadcast is sent from the set top box to the VTR so that the system interlinks according to an event in which the VTR occurs. At this time, the VTR turns on / off the power, switches the mecha mode, and converts the time code (in seconds during 'REC' and 'PLAY' and in minutes during 'FF' and 'REWIND'). When you do this, you are told to generate an event and to report to all other devices in the system.

The set top box uses a timer function to send a command to power on the VTR. The VTR sends a response indicating OK to this command request and also turns its power switch on. In addition, an event indicating that power is turned on is reported by broadcast communication to all other devices in the system, namely, set top box, personal computer, and hard disk unit.

When an event indicating that the VTR is powered on is received, the TV sets its input mode to 'VTR' by turning on its power switch. Upon receiving an event indicating that the VTR is powered on, the personal computer switches the power state of the VTR displayed on the display unit from off to on.

When the VTR receives an event indicating that power is on, the set top box sends a command to the VTR requesting the VTR to set the mecha mode to 'REC'. The VTR sends a response indicating OK for that command and sets the operation mode of the internal recording / reproducing system to 'REC'. Then, an event indicating that the mecha mode is changed to 'REC' is reported to all other devices in the system by the broadcast communication means.

Upon receiving an event indicating that the mecha mode of the VTR is set to 'REC', the personal computer changes the mecha mode displayed on the display unit to 'REC'.

The VTR generates an event whenever the time code changes in minutes and reports it to all other devices in the system using broadcast communication means. Upon receiving an event indicating that the time code has changed, the personal computer updates the time code of the VTR displayed on the display unit. The set top box also monitors whether the tape is running during timer picture recording.

5 shows a structure of an apparatus in which a subdevice takes a VTR as an example separately from other subdevices that execute centralized control of events. This VTR includes a VTR device 21 and an IEEE 1394 bus transmit / receive block 22. The VTR device 21 is provided with a VTR subdevice 23, a tuner subdevice 24, and a timer subdevice 25. They basically have the same structure as the corresponding part of the VTR shown in Fig. 10, and carry out the same operation as mentioned above.

The VTR 21 is also provided with an event processing subdevice 26 for centralized control of events. When the subdevice designated as parameter 1 for the event request command of event on / off generates an event related to the item specified as parameter 2 or 3, the event processing subdevice 26 sends this event to the IEEE 1394 bus transmit / receive block 22. Send immediately. The IEEE 1394 bus-transmit-block 22 takes the event as a packet and sends this packet to another device (controller or all other devices) required by the controller.

FIG. 6 shows an embodiment of the format of a command sent to the device shown in FIG. As shown in Fig. 6, the format is characterized in that the HA of each command is an event processing subdevice and a subdevice which generates an event is designated by parameter 1.

7 shows examples of commands and responses used in embodiments of the present invention. This command / response is referred to as a report query command / response and does not require the on / off of an event as described later, but must report a particular type of state transition (event) only once.

This report inquiry command is realized in a form added to the conventional status inquiry command. That is, the target receiving the report inquiry command means the current state in the form specified in the same manner as the response to the status inquiry command, and when the state changes thereafter, the target responds to the once converted state and is thus processed. Is completed. The CT of this command is 'Report Inquiry' and the RC of this response is 'NOW' when the current status is reported and 'CHANGED' when reporting that the status has changed.

7 (a) shows a command for requesting a status change report of the mecha mode only once. In addition, Figure 7 (b) shows a response for reporting that the current mecha mode is in the 'REWIND' state. In addition, (c) of FIG. 7 shows a response for reporting that the mecha mode is changed to 'STOP'.

8 shows that a personal computer first sends a command to the VTR requesting execution of REWIND, the VTR sends a response indicating OK for the request and simultaneously starts the REWIND in the recording / reproducing system in the VTR.

The personal computer then sends a report inquiry command shown in Fig. 7A to the VTR. Upon receiving this report inquiry command, the VTR sends the response shown in Fig. 7B.

Next, when the mecha mode changes to 'STOP', the VTR generates an event and sends a response shown in Fig. 7C to the personal computer.

Upon receiving an event from the VTR indicating that the mecha mode has changed to 'STOP', the personal computer immediately sends a command to the VTR requesting to set the mecha mode to 'PLAY'. When this command is sent, the VTR sends a response indicating OK to that command and sets the mode of the recording / playback system to 'PLAY'.

The target no longer needs to report a useless event because the report inquiry command can be used to report the required state change only when a reason is required. In addition, communication control is simpler than putting an event on / off, because a command transaction ends with a report query command and a response to this command twice. In addition, reporting on the event can be realized without significantly changing the conventional instruction processing.

1 shows examples of commands and responses used in one embodiment of the present invention.

FIG. 2 shows an application in which a personal computer acts as a controller and causes the state of the device in another mode in the system to be displayed on the display unit using the commands shown in FIG.

FIG. 3 illustrates an application for "rewinding and playing back to tape head" using the command shown in FIG.

4 shows an application example in which the command shown in FIG. 1 is sent from the set top box to the VRT and the system is connected according to the work of the VRT.

FIG. 5 is a diagram showing an example of the configuration of an apparatus in which a sub device performing central control is independent of other sub devices during operation; FIG.

FIG. 6 shows an example of the format of a command sent to a device configured as shown in FIG. 5; FIG.

7 illustrates another example of commands and responses used in embodiments of the present invention.

FIG. 8 illustrates an application for "rewinding and playing back to tape head" using the command shown in FIG.

9 illustrates an example of a communication system using an IEEE 1394 series bus.

Fig. 10 is a diagram showing an example of a data structure on a bus of a communication system using an IEEE 1394 series bus.

11 illustrates a structure of an Async communication packet including a control signal.

FIG. 12 shows an example of the configuration of a part performing an exchange of a command or a response in a device in a system; FIG.

Fig. 13 is a diagram showing a structure of a format of a command and a response and an example of a command and a response when the VTR target is used.

14 shows an application in which the personal computer acts as a controller, makes a request for the status of all other devices in the system, and displays the status on the display unit.

FIG. 15 shows an application example for "rewinding and playing back to a tape head" of a VTR. FIG.

Explanation of symbols on the main parts of the drawings

2: personal computer 11: VTR device

12: transceiver block 13: VTR subdevice

Claims (2)

A communication control method in a system in which the plurality of electronic devices are interconnected by a communication control bus for carrying a plurality of control signals and information signals between a plurality of electronic devices, Receiving a control signal indicating a command for transmitting a state of one of the plurality of electronic devices among the plurality of control signals, wherein the state change of the electronic device is predetermined; If one of the types of state changes, the command requires that the state be sent; Initiating a command transaction upon receiving the control signal; Transmitting a first response signal to at least one device that has transmitted the control signal, wherein the first response signal indicates receipt of the control signal and indicates a current state of the electronic device; Steps, Detecting a state change of the electronic device only once after receiving the control signal; When the state change is detected, transmitting a second response signal indicating the detected state change via the communication control bus, wherein the state change is only when the state change is a predetermined type specified by the command. Transmitted, transmitting the second response signal; Automatically terminating the command transaction when transmitting the second response signal. An electronic device for use in a system having the plurality of electronic devices interconnected by a communication control bus for carrying a plurality of control signals and information signals between a plurality of electronic devices. A first means for receiving one control signal indicating a command for transmitting a state of one of the plurality of electronic devices among the plurality of control signals, wherein the state change of the electronic device is a predetermined type; The first means for requesting that the state be transmitted by the first means, if one of the state changes Means for starting a command transaction upon receiving the control signal; Means for transmitting a first response signal to at least one device that transmitted the control signal, wherein the first response signal indicates receipt of the control signal and indicates a current state of the electronic device; Sudan, Second means for detecting a state change of the electronic device only once after receiving the control signal, In response to the detection by the second means, the first means sends a second response signal indicating the detected state change via the communication control bus, wherein the state change is specified by the command. Transmitted only if it is of a predetermined type, and wherein said first means automatically terminates said command transaction when transmitting said second response signal.