CM109 Datasheet, PDF (26/36 Pages) C-Media Electronics – USB I/O Controller

CM109
High Integration / Low Cost USB Audio Controller
for PC Internet Phone
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 detailed about
acknowledgement bit. Note that ‘SCLK’ is always driven by the master.
SDAT
MSB
Acknowledgement
Signal from Receiver
P
Acknowledgment
Sr
Signal from Receiver
SCLK
S
or
Sr
1
2
START or Repeated
START Condition
7
8
9
ACK
1
2
3-8
9
ACK
Data Transfer on the MCU Interface
Sr
or
P
STOP or Repeated
START Condition
The figure below shows a complete data transfer. After a START, MCU should send
7-bit slave address (7’b0111000) first, and then the 8th bit denotes a read transfer when
it’s high; or a write transfer when it’s low. The first acknowledgement is always from
CM109.
Date: 08/Sep/2005
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Version: 1.3a