CM6327A
USB Single-Chip Audio Solution for Mono Microphone
7.1.2 Slave Mode
“7-bit slave address = 7’b0111000”
On the MCU serial interface, the CM6327 serves as a slave device with bit rate up to 400Kbps (fast mode).
The MCU can write data to the CM6327A or read data from the CM6327A (no size limitations when using the
I2C Interface). Since the host side and MCU both have access to all the internal registers, access contention
when both host and MCU try to access the same register should be avoided upon application. The CM6327A’s
7-bit slave address is assigned as 7’b0111000.
When data is written by the MCU, the CM6327A will NOT transfer any interrupts to the PC until the INT bit of
the I2C control register has been set by the MCU. The USB host will keep polling the upward HID report every
1ms. When any button is pressed or released, or there is incoming MCU data, the CM6327A will transfer 16
bytes of HID report to the USB host.
In I2C Slave Mode, the CM6327A has one open-drain input pin (SCLK) from where it receives the serial clock
from the MCU, and one open-drain I/O pin (SDAT) from 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).
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