CM108AH Datasheet, PDF (19/27 Pages) C-Media Electronics – Highly Integrated USB Audio I/O Controller

CM108AH
Highly Integrated USB Audio I/O Controller
7.4 Internal Registers
All of CM108AH’s internal registers can be accessed via generic HID functional calls without the need to
develop a kernel mode driver. In total, 4 bytes of data can be read or written from the HID. The input report is
for read and the output report is for write. These internal registers of are used to control GPIO pin, S/PDIF
output and EEPROM data access.
HID_IR0 (HID input report byte 0)
Offset: 0x00
Bits
Read/Write
Description
7-6
R
00: HID_IR1 is used as GPI,
10: values written to HID_IR0-3 are also mapped to
EPROM_DATA0-1 and EEPROM_CTRL
Others: reserved
5-4
R
Reserved
3
R
0: no activity on record/mute button
1: record/mute button pressed then released
2
R
0: no activity on playback/mute button
1: playback/mute button pressed then released
1
R
0: volume-down button released
1: volume-down button pressed
0
R
0: volume-up button released
1: volume-up button pressed
Default
0x0
0x0
0x0
0x0
0x0
0x0
HID_IR1 (HID input report byte 1)
Offset: 0x01
Bits
Read/Write
Description
Default
When HID_IR0[7:6] == 2’b00: HID_IR1[3:0] is the input from
7-0
R
GPIO4 ~ GPIO1 in input mode
0x00
When HID_OR0[7] == 1’b1: mapped from EEPROM_DATA0
HID_IR2 (HID input report byte 2)
Offset: 0x02
Bits
Read/Write
Description
7-0
R
When HID_OR0[7] == 1’b1: mapped from EEPROM_DATA1
Default
0x00
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