CM6206 Datasheet, PDF (20/35 Pages) C-Media Electronics – High Integrated USB Audio I/O Controller

CM6206
High Integrated USB Audio I/O Controller
6.2 MCU Interface
CM6206 can communicate with external MCU via two-wire serial interface and act as a slave device. By
this way, MCU can read four bytes from and write two bytes to USB host through CM6206. When MCU
writes two bytes to CM6206, the data will be transferred to USB host via HID ‘Input Report’. USB host will
keep polling HID report every 1ms. CM6206 can also transfer four bytes from USB host to MCU. This is
accomplished by a ‘Set Output Report’ HID request issued by USB host.CM6206 will then assert MINT to
inform MCU to read them.
CM6206 has one input pin ‘SCLK’ to get serial clock from MCU, and one open-drain output pin ‘SDAT’ to
send or receive serial signal to/from MCU. As shown below, ‘SDAT’ should be stable when ‘SCLK’ is high,
and can have transition only when ‘SCLK’ is low.
Figure 6-1. IIC data to clock protocol
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).
Figure 6-2. IIC start/stop condition protocol
The figure below demonstrates a transaction example. 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.
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