CM6308 C-Media Electronics, Inc., CM6308 Datasheet - Page 26

• 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
7.2.3
The Serial Interface
The serial data is read from the serial data input pin on the rising edge of the serial clocks D7,
D6 through D0, in this order. This data is converted to 8 bits of parallel data on the rising edge
of the eighth serial clock cycle for the processing. The A0 input is used to determine whether or
not the serial data input is displaying data or command data; when A0 = “H”, the data is display
data, and when A0 = “L” then the data is command data. The A0 input is read and used for
detection every 8th rising edge of the serial clock after the chip active. Figure 1 is a serial
interface signal chart.
When the CM6308 acts as a SPI slave, the external MCU can read/write registers within the
CM6308 through the SPI interface. Each transaction is 3-bytes long. The first byte is a
read/write command indicator. Once the MSB of the first byte is low, it means a read
transaction is occurring; otherwise it is a write transaction. The other bits of the first byte are
meaningless. The second byte is the address of the desired register. The third byte, for a read
transaction, is meaningless, and meanwhile the MISO would output the data of register. The
third byte, for write transactions, is data.
Date: 09/04/2007
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