CM6308 C-Media Electronics, Inc., CM6308 Datasheet - Page 18

• Manufacturer Part Number: CM6308
• Description: Cm6308 Usb Audio Chip Specification
• Manufacturer: C-Media Electronics, Inc.

CM6308
Single-Chip USB Solution for
Audio and Voice Applications
The USB host will keep polling the upward HID report every 1ms. When any button is pressed
or released, or MCU data is incoming, the CM6308 will transfer 16 bytes of HID report to the
USB host. In I2C Slave Mode, the CM6308 has one open-drain input pin ‘SCLK’ where it
receives the serial clock from the MCU, and one open-drain I/O pin ‘SDAT’ where it sends or
receives serial signals to/from the MCU. As shown below, ‘SDAT’ should be stable when ‘SCLK’
is high, and can transition only when ‘SCLK’ is low.
START and STOP conditions shown below are the exception. Every transaction begins from a
START, and ends with a STOP, or another START (repeated START).
The figure below demonstrates a typical transaction. After every 8 bits sent by the transmitter,
the receiver should send one bit low for positive acknowledgement or one bit high for negative
acknowledgement. After the negative acknowledgement, a STOP or repeated START should
follow. The next figure shows more details about the acknowledgement bit. Note that ‘SCLK’ is
always driven by the master.
Date: 09/04/2007
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