CMI8788 骅讯电子PCI 32位多声道音频处理器

　　Description and Overview

　　The CM18788 is a high quality PCI 32-bit multi-channel audio processor that can be built into home audio electronics or personal computers to provide high fidelity sound playback and processing. It supports up to 12 output channels and 8 input channels. The 12 output channels are composed of 3 playback DMA's, which are multi-channel DMA (32 bits, 8 channels, 192k),S/PDIF DMA (32 bits,2 channels, 192k), and front panel DMA (16 bits, 2 channels, 48k). The 8 input channels are spread across 3 recording DMA's (32 bits, 192k) -recording A, B, and C DMA's. The architecture of recording is a unique point of CMI8788 that enables very flexible recording options for the user. The details of the recording mode selection will be explained in the later sections.

　　The CM8788 is compatible with all the popular codecs, from 12S codecs with over 120dB quality to the usual AC97 codecs. This ability gives customers the flexibility to design their products exactly the way they want them. The I2S, AC-Link, 2-wire master bus, and SPI interfaces are used to transfer audio data and control data between the CM8788 and codecs. To facilitate the connection with existing home audio electronics, the CM8788 has incorporated the S/PDIF transmitter and receiver with 192k sampling rate.

　　An EEPROM interface is built for the CM18788 in connection with the EEPROM to store and retrieve the non-evaporable data for customer applications, such as board configuration, sub-vendor and sub-system IDs of the PCI configuration, or any dynamic data that customers want to restore at the next power-on.

　　The CM8788 has an independent 2-wire slave bus to communicate with the micro control unit (MCU).This interface is used as a medium for the system driver and the MCU to exchange data. One of the applications of the 2-wire slave bus is to transmit the control data from the remote controller to the system driver. The MPU-401 MIDI UART is also integrated in the CMI8788.

　　There are six GPI phone jack detect pins in CMI8788, which can be used to distinguish if a cable is plugged in the phone jack. There are 9 GPIO pins on the chip, however some of them are shared with other functions. The C-Media's unique device sensing technology is implemented inCMI8788,which can indicate whether a speaker or a headphone is plugged in the jack. Then according to this information, the system driver can decide to turn on the C-Media's X-ear 3D audio technology if appropriate.