CM109 Datasheet, PDF (24/36 Pages) C-Media Electronics – USB I/O Controller

CM109
High Integration / Low Cost USB Audio Controller
for PC Internet Phone
EEPROM_DATA0 (Low byte of EEPROM data)
Offset : 0x09
Bits Read/Write
Description
7-0
R/W Low byte of EEPROM data to be accessed
Default
0x00
EEPROM_DATA1 (High byte of EEPROM data)
Offset : 0x0a
Bits Read/Write
Description
7-0
R/W High byte of EEPROM data to be accessed
Default
0x00
EEPROM_CTRL (Serial EEPROM access control)
Offset : 0x0b
Bits Read/Write
Description
7
R/W When Register Read:
0: No EEPROM access pending
1: Last EEPROM access pending
When Register Write:
0: No action
1: Start EEPROM access (will clear to 0
automatically)
6
R/W 0: Read EEPROM
1: Write EEPROM
5-0
R/W Address of serial EEPROM
Default
0x0
0x0
0x00
7.5 MCU Interface
On MCU serial interface, CM109 serves as a slave device with bit rate up to 400Kbps
(fast mode). MCU can read/write 3 bytes to CM109 device with a 2-bit register address.
Since host side and MCU can both access to all the internal registers, access contention
when both host and MCU try to access the same register should be avoided on
application. The 7-bit slave address of CM109 is assigned as 7’b0111000.
When a one-byte data is written by MCU, CM109 will transfer totally 4 bytes to the USB
host via an additional interrupt pipe. The sequence of the upward HID report is the
button status first (address 00), then register with address 01, then register with address
02, then register with address 03. The USB host will keep polling the upward HID
Date: 08/Sep/2005
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Version: 1.3a