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Abstract: CD/DVD ROM has become the standard equipment for portable computers. The OZ168 chip uses AudioDJTM technology to ensure that CD music can be enjoyed without the computer being turned on, thus turning the portable computer into a CD player that can be carried. Greatly reduce computer battery consumption and maximize working hours. The main characteristics, structure and function of OZ168 are introduced in this paper, and the application circuit is given.Keywords : AudioDJTM technology; CD playback; laptop
1 Introduction
OZ168 is a dedicated portable computer audio player chip produced by O2 MICRO. At present, almost all portable computers use CD/DVD ROM as a standard configuration. Under normal circumstances, playing CD music on a portable computer requires first booting the system and playing it with Window-sTM Media Player or other media playback software. For a simple function to turn on the system, and consume a lot of battery power, this will undoubtedly bring the pressure of battery power shortage for normal mobile office. AudjoDJTM technology enables portable computer users to enjoy the beauty of CD music at any time without worrying about battery capacity limitations. The dedicated power-shielding measures of OZ168 devices ensure that only a small part of the system working power such as CD/DVD ROM is provided. Turn off, which greatly reduces the battery consumption of the computer and maximizes battery operating time. Figure 1 is a block diagram of the OZ168's working system. Its main functions and features are as follows:
   ◠has three working modes: CD play mode, direct play mode, direct communication mode;
â—Three power management schemes: automatic power saving working mode, sleep mode, standby mode;
â— Support 2-digit CD track digital display, LCD can display STOP, Play? Pause? Search and other status;
â— In the CD playback mode, the various working states of the CD/DVD ROM can be controlled by the ATAPI protocol;
â— Support CD/DVD ROM DMA function, so the data transmission rate is faster;
â—AudjoDJTM technology ensures minimal software support for the system;
â— With CD high quality sound effects.
2 working mode
The OZ168 has three working modes: CD Player Mode, Direct Mode and PASS Through Mod. Moreover, the chip automatically enters the corresponding working mode according to different working states of the computer.
2.1 CD playback mode
When the system is in CD playback mode, only the CD ROM and the audio amplifier need power supply in the whole system, and the rest of the system is turned off. At this time, the left and right channel audio signals of the CD ROM are directly transmitted to the audio amplifier, thereby ensuring that the power is not turned on. Play the CD down. In CD Player mode, the OZ168 can directly control the status of the CD/DVD ROM and play the tracks of the CD Track through the ATAPI protocol. The OZ168 music play button functions are as follows:
(1) By playing Player, Pause, NEXT TPK, PREV TRK, STOP EJ ECT, etc., users can select their favorite music.
(2) Through the ATAPI interface, the working state of the CD ROM can be controlled directly through the ATAPI command in the CD Player working mode. ATAPI can provide the control commands listed in Table 1, as well as some control commands. ATAPI devices such as CD/DVD ROM support all ATA-specific protocols and control commands in OZ168 operation. Figure 2 is a diagram showing the operation state of the CD playback mode.
Table 1 ATAPI Command Control Table
| Command control | Operation code |
| Mode sense | 5Ah |
| Pause/resume | 4Bh |
| Play audio MSF | 47h |
| STOP | 1Bh |
| Read TOC | 43h |
| Request sense | 03h |
| Read sub channel | 42h |
| Test unit ready | 00h |
| Unlock | 1Eh |
2.2 Direct play mode
In the direct play mode, the system has actually entered the power-on state, and the user can still control the CD play with various function keys. When the function keys PLAY PAUSE, NEXT TRK, PREV TRK or STOP_EECT are pressed, the OZ168 will issue an interrupt INT signal to change the 8th byte of the interrupt status register ?07h?. When the OZ168 has an INT signal, SMBUS Host will read the function key register ?01h? to determine which key is pressed, after which the Bit?ACK? byte of the command control register ?03h will be reset, the predetermined AudioDJTM driver and CD ROM The driver will issue corresponding control commands directly to the CD/DVD ROM to control the action of the CD/DVD ROM. When the OZ168 control command ends, the OZ168 will automatically clear the value of the function key register and ACK byte.
2.3 Straight channel mode
In the PASS Through mode, the OZ168 is treated as a transparent part between the OS and all system devices, that is, the device and the OS both “see†the existence of the OZ168. At this time, the OZ168 only transmits all the connections between the system and the CD ROM. And feedback commands, and OZ168 does not make any changes to these instructions and data, all system IDE bus signals are passed directly to the CD ROM IDE bus. At this time, the OZ168 is only used as a channel for data/command transmission between the system and the CD ROM. 3 internal structure
The internal structure of OZ168 is shown in Figure 3. The main components of the OZ168 are described below.
3.1 State Controller Module
The three operating states of the OZ168 are primarily selected by the state controller, which determines which mode of operation is entered by detecting the input signals of PAV EN, PC SYSTE-MOFF(), and Direct Mode register(). When PAV_EN is 1 and PC SYSTE-MOFF is 1, OZ168 will issue PWR CTRL signal to turn on the power of CD ROM and audio amplifier, and cooperate with function key controller to directly control the working state of CD ROM through ATAPI protocol. At this time, OZ168 enters. CD Player mode. The input logic signals and associated states of the state controller module are listed in Table 2.
Table 2 Status controller and working mode status table
| Operating mode | PAV-EN signal status | PCSYSTEM-OFF signal status | Direct Mode signal status |
| CD Player | 1 | 1 | x |
| Direct Mode | x | 0 | 1 |
| Pass Through | x | 0 | 0 |
| Power Off | 0 | 1 | x |
3.2 Function Key Control Module
In CD Player mode and Direct mode, when a function key signal is input to the control module, the function key controller will refill the internal register and transfer the changed register information to the status controller module. The status controller receives and saves these settings and converts them to ATAPI protocol control commands to directly control the CD/DVD ROM for various function selections.
3.3 LCD status display module
The OZ168 uses COM0, COM1 and LCD?12...1? signals to drive the LCD 2-digit 7-segment digital tube to display the current number of tracks and the status of STOP, PLAY, PAUSE and Fast search. COM0 and COM1 are the 12th group of 64Hz clock drive signals of the LCD panel display module. Use LCD? 12...1?12-bit display data signal, and cooperate with COM0, COM1 clock signal to drive 3-digit 7-segment digital tube. Figure 4 shows the waveforms of the clock drive signals of COM0 and COM1.
4 design examples
OZ168 voltage range is -0.3V ~ +6.0V, its input voltage should be between -0.3 ~ +0.3V, the normal operating temperature range is 0 ~ 70 °C. Figure 5 is an application example of OZ168. Its function key input signals PREV TRK, NEXT TRK, PLAY PAUSE, STOP EJECT, etc. need to be connected with 100pF filter capacitor to prevent malfunction caused by noise interference. PWR CTL signal is connected to 47kΩ pull-down. The resistor can ensure that the PWR CTL is 0 at the rising edge of RESET, thus turning on the power management control. The PAVMODE/IDSEL pin should also be connected to the 4.7kΩ resistor. Selecting the SM BUS address ID to 34h ensures that the input power of the OZ168 is stable. A 10μF tantalum capacitor and a 0.1μF ceramic capacitor are required for the power coupling circuit.
Figure 5
5 Conclusion
The OZ168 audio playback circuit designed in this paper can be used as a reference design circuit. The digital volume adjustment function is not implemented in the design without using GPIO[1:0]/VOL_UP/VOL_UP signal external digital potentiometer. Due to the advanced power management technology, OZ168's power consumption is very low, its high compatibility ATAPI interface specification can be applied to various brands of CD/DVD ROM? For OEMs, CD/DVD ROM configuration can also be changed according to different needs, but it does not affect PC compatibility, which brings great convenience to system configuration. At the same time, it also provides users with more upgrade space.
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