C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
1
Ver. 1.2
With high speed PCI V2.1 bus controller and legacy audio
SB16® DSPemulator,CMI8738 is designed for PC add-in cards
and all-in-one motherboards. No external CODEC is needed in
CMI8738: CMI-8738 supports the legacy audio – SB16™, FM
emulator/DLS wavetable music synthesis, and HRTF 3D
positional audio functions.
Being compatible with A3D™ and DirectSound™ 3D, CMI8738
meets PC99® requirements
CMI8738 uses HRTF 3D extension technology to enhance
traditional HRTF 3D positional audio by substituting two-speaker
system by four- speaker one (it supports additional 2CH 16-bit
DAC to provide rear side audio). It greatly improves HRTF 3D
positional audio quality and successfully removes the sweet spot
limitations: users can enjoy genuine 3D audio gaming effects,
and don't have to worry about the environmental confinement any
more.
Being outstanding for its full audio functions, competitive price,
and power management, CMI-8738 is the best choice for people
seeking for optimum use of the PC applications.
C-Media licensed HRTF 3D library from Central Research
Lab (CRL®), U.K, who provides one of the world's best HRTF
libraries
Features
HRTF-based 3D position al audio,
supporting DirectSound™ 3D and A3D™
interface
Supports rear side speakers, C3DX
positional audio in 4 CH speaker mode
Legacy audio SBPro™ compatible
DLS-based wavetable music synthesizer,
supports DirectMusic™
Built-in 32ohm Earphone buffer
Drivers support EAX™, Karaoke Echo , Key
Surround sound
MPU-401 port
Dual game port
16-bit full duplex CODEC
4 CH 16-bit DA C
32-bit PCI bus master
External E²PROM interface
Single chip design, +5V, 128 pins QFP
Preliminary Ver 1.2
CMI-8738/PCI-SX
C3DX PCI-Based HRTF 3D Extension Positional Audio Chip
CMI-8738/PCI Block Diagram
PCI interface
PCI BUS
DMA engine
IRQ control
Legacy audio
SB16™emulator
MPU 401 and
GAME port
Music Synthesizer
HRTF DSP engine
16-bit CODEC
Analog Mixer
PLL and
timing circuit
14.318Mhz
3D
Surround
Earphone
buffer
LINE
OUT
MIC AMP
LINE / CD /
AUX / PCPSK
IN
MIC IN
Rear
L/R
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
2
Ver. 1.2
U1
CMI8738
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
101
100
99
98
97
96
95
94
93
92
91
90
89
88
87
86
85
84
83
82
81
80
79
78
77
76
75
74
73
72
32
33
34
35
36
37
38
39
40
41
42
43
44
128
127
126
125
124
123
1
65
66
67
68
69
70
71
102
NC
NC
NC
NC
NC
NC
XBIO3
XBIO2
XBIO1
XBIO0
NC
GND
VDD
GND
XINTA
NC
XPRST
XCLK33
XGNT
XREQ
XADOUTL
XVREF
XINTVREF
AVDD
AGND
NC
NC
NC
XOUT
XIN
VDD
GND
XA0
XA1
XA2
XA3
XA4
XA5
GND
VDD
XA27
GND
VDD
XA26
XA25
XA24
XCBE3
XIDSEL
VDD
GND
XA23
XA22
XA21
XA20
XA19
GND
VDD
XA18
A17
XA16
XCBE2
XFRAME
XIRDY
XTRDY
XDEVSEL
VDD
GND
XSTOP
XPAR
XCBE1
NC
VDDM
DGND
NC
XGD7
XGD6
XGD5
XGD4
XGD3
XGD2
XGD1
XGD0
XRXD
XTXD
XGPBIO
NC
XMBCSZ
XEECS
VDD5V
AGND
AVDD
XMICIN
XPCSPKIN
XAUXR
XAUXL
XLNR
XLNL
XREARR
XREARL
XCDR
XA15
XA14
XA13
XA12
GND
VDD
XA11
XA10
XA9
XA8
XCBE0
XA7
XA6
XA29
XA30
XA31
GND
VDD
NC
XA28
XADOUTR
XADCHL
XADCHR
XLFILT
XRFILT
XCDGND
XCDL
NC
PINOUT
PINOUT
CMI8738-037-SX AUDIO CHIP
QFP 128 PINS
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
3
Ver. 1.2
DIGITAL PIN DESCRIPTION
Name Number PIN
Type Definition
XA31-XA0 126-128,1-2,5-7,12-16,19-21,32
-35,38-41,43-44,47-52 I/O PCI bus address and data lines
XINTA 117 O Interrupt request , activ e-low.
XPRST 119 I Reset
XCLK33 120 I PCI bus clock.
XGNT 121 I Bus master grant, activ e-low.
XREQ 122 O Bus master request, tri-state
output, active-low.
XIDSEL 9 I ID select, active-high.
XFRAME 23 I/O Cycle frame, active-low.
XIRDY 24 I/O Initiator ready, active-low. The bus
master device is ready to transmit
or receive data
XTRDY 25 I/O Target ready, active-low. The target
device is ready to transmit or
receive data
XDEVSEL 26 I/O Device select, active-low. The
target device has dec o ded the
address of the current transaction
as its own chip select range.
XSTOP 29 I/O Stop transaction, active-low. The
target device reque st to the master
to stop the current transaction.
XPAR 30 I/O Parity. The pin indicates even parity
across XA31-XA9 and XCBE3-0 for
both address and data phases.
XCBE3,2,1,0 8,22,31,42 I/O Multiplexed command/byte enable.
These pins indicate cycle type
during the address phase of a
transaction.
VDD 4,10,18,27,37,45,54,115,124 +5V Digital and PCI I/O power pin
GND 3,11,17,28,36,46,53,114,116,12
5 GND Digital and PCI I/O ground
XIN 55 I 14.318Mhz cry stal, or external clock
input
XOUT 56 O 14.318Mhz crystal
XGD7-XGD4 97-94 I Game port switch input pin.
Switch D to switch A
XGD3-XGD0 93-90 I/O Game port resistor input pin.
RC3 to RC0
XTXD 88 O MIDI transmit data
XRXD 89 I MIDI receive data
XBIO3-XBIO
0 109-112 I/O General purpose I/O
VDD5V 83 +5V Digital and PCI I/O power pin
VDDM 100 +5V Digital and PCI I/O power pin
DGND 99 GND Digital and PCI I/O ground
XEECS 84 O EEPROM chip select
PIN DESCRIPTION
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
4
Ver. 1.2
AVDD 61,81 +5V Analog power
AGND 60,82 GND Analog ground
XADOUTL-R 64,65 AO1 Line out
XADCHL-R 66,67 AI/O ADC filter
XLFILT 68 AI/O Left channel DAC filter
XRFILT 69 AI/O Right channel DAC filter
XVREF 63 AI Reference Voltage (no u se, left it
floating)
XINTVREF 62 AI Reference Voltage
XCDL-R
XCDGND 71,72,70 AI CD audio differential input
XLNL-R 75,76 AI Line in or Rear speaker out
XAUXL-R 77,78 AI Aux. Line in
XPCSPKIN 79 AI PC beep signal
XMICIN 80 AI Microphone in
XREARL-R 73,74 AI/O Rear speaker out
XGPBIO 87 O General purpose I/O pin
XMBCSZ 85 I Audio chip select (lo w:enable)
NC 57-59,86,98,101-108,113,118,1
23 - Reserved
PIN DESCRIPTION
ANALOG PIN DESCRIPTION
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
5
Ver. 1.2
ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings
Ratings Symbol Value Units
Digital power voltage VDD VDD±5% V
Analog power voltage AVDD AVDD±5% V
Operating temperature range TO 0 to 70 °C
Storage temperature range TST -40 to 125 °C
Maximum power dissipation PDMAX 300 MW
Digital Characteristics
PARAMETER Symbol Min Typ Max Unit
Input high voltage(PCI I/O) VIH 2. VDD+0.5 V
Input low voltage (PCI I/O) VIL -0.5 0.8 V
Output high voltage VOH 2.4 VDD V
Output low voltage VOL 0.0 0.2 0.4 V
Output buffer current 5 mA
Audio Characteristics
PARAMETER Symbol Min Typ Max Unit
Analog input voltage Avin 1.1 VRms
Analog output voltage Avout 1.1 VRms
A-A S/N ratio 85 db
A-A THD 0.09
ADC S/N ratio 80 db
ADC THD 0.1 0.2 %
DAC S/N ratio 80 db
DAC THD 0.1 0.2 %
Microphone input level 20 200 mv
Microphone booster 20 db
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
6
Ver. 1.2
CMI8738 PCI Configuration Spaces
00h 13F6 : (Vender ID) read only
02h 0111 : (Device ID) read only
04h 0006 : Command (State after #RST all is “0”)
0 (bit 9) Fast back-to-back enable
0 (bit 8) #SERR enable (R/W)
0 (bit 7) Wait cycle control
0 (bit 6) Parity error response
0 (bit 5) VGA palette snoop
0 (bit 4) Memory write and invalidate enable
0 (bit 3) Special cycles
1 (bit 2) Bus master (R/W)
0 (bit 1) Memory space
1 (bit 0) I/O space (R/W)
06h 0280 : Status
0 (bit 15) Detected Parity Error
0 (bit 14) Signaled System Error
0 (bit 13) Received Master Abort
0 (bit 12) Received Target Abort
0 (bit 11) Signaled Target Abort
01 (bits 10-9) DEVSEL timing 00-fast, 01-medium, 10-slow
0 (bit 8) Data Parity Error Detected
1 (bit 7) Fast Back-to-Back Capable
0 (bit 6) UDF Supported
0 (bit 5) 0-33MHz ,1-66MHZ Capable
00000 (bits 4-0) Reserved
08h 10 : Revision ID
09h 040100 : Audio device
0Ch 00 : Cache Line Size
0Dh 20 : Latency Timer
0Eh 80 : Header Type
0Fh 00 : BIST
Configuration
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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
7
Ver. 1.2
10h 0000d401 : I/O of length : -65280(ffff0100h) : First Base Address register
14h 00000000 : Uninitialized : Second Base Address register
18h 00000000 : Uninitialized : Third Base Address register
1Ch 00000000 : Uninitialized : Fourth Base Address register
20h 00000000 : Uninitialized : Fifth Base Address register
24h 00000000 : Uninitialized : Sixth Base Address register
28h 00000000 : Cardbus CIS Pointer
2Ch 13f6 : (SubSystem Vender ID) (R/W)
2Eh ffff : SubSystem ID (R/W)
30h 00000000 : Expansion ROM Base Address
34h 00000000 : Reserved
38h 00000000 : Reserved
3Ch 05 : Interrupt Line
3Dh 01 : Interrupt Pin
3Eh 02 : Min Grant
3Fh 18 : Max Latency
DMA Slave Configuration Register(R/W) PCI Configuration address 40H
Bit(s) Function
31:16 Reserved
15:4 Slave Base Address 15-4. INTEL VX chipset seleted if Base Address
15:4=000h
3 Non legacy Extended Addressing
0 = disabled
1 = enabled
2:1 Transfer Size
00 = 8 bit transfer
01 = 16 bit transfer
10 = 32 bit transfer, non legacy
11 = Reserved
0 Channel Enable
0 = disabled
1 = enabled
Configuration Configuration
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
8
Ver. 1.2
Internal Register Mapping
Function Control Register 0
Address 00H
Bit(s) R/W Name Description
31-20 Reserved.
19 RST_CH1 Channel1, 1->Reset (Default 0)
18 RST_CH0 Channel0, 1->Reset (Default 0)
17 CHEN1 Channel1, 1->Enabled, 0->Disabled.
16 CHEN0 Channel0, 1->Enabled, 0->Disabled.
15-4 Reserved
3 PAUSE1 Channel1, 1->Pause if channel1 is enabled.
2 PAUSE0 Channel0, 1->Pause if channel0 is enabled.
1 CHADC1 Channel 1 , 1->Recording, 0->Playback
0 CHADC0 Channel 0, 1->Recording, 0->Playback
Function Control Register 1
Address 04H
Bit(s) R/W Name Description
31-16 Reserved
15-13 DSFC[2:0] DAC Sampling Frequency Select,
0 0 0 5.512 K
0 0 1 11.025 K
0 1 0 22.05 K
0 1 1 44.1 K
1 0 0 8 K
1 0 1 16 K
1 1 0 32 K
1 1 1 48 K
12-10 ASFC[2:0] ADC Sampling Frequency Select,
0 0 0 5.512 K
0 0 1 11.025 K
0 1 0 22.05 K
0 1 1 44.1 K
1 0 0 8 K
PCI register
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
9
Ver. 1.2
1 0 1 16 K
1 1 0 32 K
1 1 1 48 K
9-6 Reserved
5 INTRM Interrupt Mask bit for MCB (Master control block) module interrupt.
0 MCB interrupt disabled.
1 MCB interrupt enabled.
4 BREQ If this bit is set low it will prevent the MCB and DAC/ADC block
from accessing the memory.
0 Bus Master request disabled(power on state)
1 Bus Master request enabled.
3 VOICE_EN This bit enables Legacy Voice device(SB16,FM).
0 Legacy Voice disable d on channel 0.
1 Legacy Voice enabled on channel 0.
2 UART_EN This bit enables Legacy UART device.
0 UART disabled
1 UART enabled
1 JYSTK_EN This bit enables Legacy Joystick device.
0 Joystick disabled
1 Joystick enabled
0 Reserved
Channel Format Register
Address 08H
Bit(s) R/W Name Description
31-24 VER[7:0] PCI Audio subversion for internal indentification. “01”
23-19 Reserved
18 FMOFFSET2 When set 1 and Reg. 24H bit7 ‘FMmute=1’,FM PCM will be forced
to DC value 0002H.
17-16 Reserved
15-14 AdcBitLen[1:0] Sample resolution
00 16 Bits per sample . (Default)
01 15 Bits per sample.
10 14 Bits per sample.
11 13 Bits per sample.
13-12 AdcDacLen[1:0] Sample resolution
00 600nSec per bit in a sample.
01 660nSec per bit in a sample.
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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
10 1.3uSec per bit in a sample. (Default)
11 2.8uSec per bit in a sample.
11 CH1 Ssmple Rate 176K
10 CH1 Sample Rate 88K
9 CH0 Sample Rate 176K
8 CH0 Sample Rate 88K
7-4 reserved
3-2 CH1FMT[1:0] Data format of channel 1
00 8 bit Mono mode
01 8 bit Stereo mode
10 16 bit Mono mode
11 16 bit Stereo mode
1-0 CH0FMT[1:0] Data format of channel0
00 8 bit Mono mode
01 8 bit Stereo mode
10 16bit Mono mode
11 16 bit Stereo mode
Interrupt Hold/Clear Register
Address 0CH
Bit(s) R/W Name Description
31-19 Reserved
18 TDMA_INT_EN Interrupt hold/clear bits for updating TDMA position
0 Interruupt Clear
1 Interrupt Hold if exist.
17 CH1_INT_EN Interrupt hold/clear bits for the Channel 1.
0 Interrupt Clear
1 Interrupt Hold if exist.
16 CH0_INT_EN Interrupt hold/clear bits for the Channel 0.
0 Interrupt Clear
1 Interrupt Hold if exist.
15-0 Reserved
Interrupt Register
Address 10H
Bit(s) R/W Name Description
31 R INTR Interrupt reflected from any sources.
0 No interrupt
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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
1 Interr upt pending
30-28 Reserved
27 R VCO
26 R MCBint Abort conditions occur during PCI Bus Target/Master Access.
0 No interrupt
0 Interr upt pending
25-17 Reserved
16 R UARTint This bit is the UART interrupt bit.
0 No UART interrupt
1 UART interrupt pending
15 R LTDMAINT Inter r upt fo r u pdat i ng Low Channel TDM A position.
0 No interrupt
1 Interrupt pending
14 R HTDMAINT Interrupt for updation Hi g h C han nel TDM A position.
0 No interrupt.
1 Interrupt pending.
13-8 Reserved
7 R XDO46 Direct programming EEPROM interface , read data register
6 R LHBTOG High/Low status from DMA CTRL register.
5 R LegHDMA Legacy is in High DMA channel.
4 R LegStereo Legacy is in Stereo mode.
3 R Ch1Busy Channel B Busy.
2 R Ch0Busy Channel A Busy.
1 R Chint1 Channel B Interrupt.
0 No interrupt
1 Interr upt pending
0 R Chint0 Channel A Interrupt.
0 No interrupt
1 Interrupt pending
Legacy Control/Status Register
Address 14H
Bit(s) R/W Name Description
31 Reserved
30-29 VMPU [1:0] Base address for MPU401 access
00 Base address : 330h
01 Base address : 320h
10 Base address : 310h
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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
11 Base address : 300h
28 Reserved
27-26 VSBSEL[1:0] The Base Address Select for SB16 access.
00 Base address: 220h
01 Base address: 240h
10 Base address: 260h
11 Base address: 280h
25-24 FMSEL[1:0] The Base Address Select for FM access.
00 Base address : 388h
01 Base address : 3C8h
10 Base address : 3E0h
11 Base address : 3E8h
23-21 Reserved
20 SetRetry Mode of wait state . 0:legacy I/O wait (default) 1:legacy I/O BUS
retry
19 C_EEACCESS Direct programming EEPROM interface Registers.
18 C_EECS
17 C_EEDI46
16 C_EECK46
15-0 Reserved
Micellaneous Control Register
Address 18H
Bit(s) R/W Name Description
31 PWD Power Down Mode enabled..
30 RESET Reset Bus Master/DSP Engine.
29-28 SFIL[1:0] Four level of filter control at the front end DAC..
27 TX/VX Which motherboard to work with
0 VX chip sets.
1 TX chip sets.
26 N4SPK3D Hardware copy front channel to rear channel
25-24 Reserved
23 ENDBDAC Default low, High will enable Double DAC structure.
22 XCHGDAC Default low,
0 CH0 > Front SPKR, CH1 > Back SPKR.
1 CH0 > Back SPKR, CH1 > Front SPKR.
21-20 Reserved
19 FM_EN Legacy FM enabled.
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
18-17 Reserved
16 VIDWPDSB Sub ID write protect disabled. (default 0)
15 Reserved
14 MASK_EN Activate channel mask on Legacy DMA.
0 Disabled
1 Enabled
13 VIDWPDSB Write Protect of HSP Configuration Sub ID.
0 Protect.
1 No protect.
12 SFILENB Let software contrl filter stepping at the front end DAC.
11-5 Reserved
4 MIDSMP Enable 1/2 interpolation at th e Front end DAC..
3-2 UPDDMA[1:0] For every the number of samples to notify updating TDMA position.
00 Every 2048 samples
01 Every 1024 samples
10 Every 512 samples.
11 Every 256 samples.
1-0 TWAIT[1:0] For controling the length of legacy BUS cycle.
00 3 PCICLK.
01 18 PCICLK.
10 24 PCICLK
11 32 PCICLK
* Notice REQ_SQ[2:0] States of BusRequest Engine.
MM_DATA Bus Master is using Bus.
MIDLE Bus Master is not using Bus.
REQA/REQB Channel 0/1 BusMaster Request.
GNTA/GNTB Channel 0/1 BusMaster Grant.
ADRQ/BDRQ Channel 0/1 DMA Request.
ADACK/BDACK Channel 0/1 DMA Acknoledge.
AIRQ/BIRQ Channel 0/1 Interrupt.
CX/BX Channel 0/1 Busy.
T - DMA Position
Address 1CH
Bit(s) R/W Name Description
31-16 R TDMACN T Current Byte/Word Count of DMA channel.
15-0 R TDMAADR Current Address of DMA channel.
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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
Mixer Control / Device Configure Register (can be accessed only by BYTE instruction)
Address 20H
Bit(s) R/W Name Description
7-0 W SBVR[7:0] Programmable SB16 version No.
R DEV[7:0] Hardwire device version No.
Address 21H
Bit(s) R/W Name Description
7-3 Reserved
2 X_ADPCM SB16 ADPCM enable,default disabled.
1 PROINV SBPro Left/Right channel switching.
0 X_SB16 Indicate device active as SB16 compatible, default SB16
Address 22H
Bit(s) R/W Name Description
7-0 IDXdata Mapping SB compatible mixer INDEX register data port(A2x5h)
Address 23H
Bit(s) R/W Name Description
7-0 IDXaddr Mapping SB compatible mixer INDEX register address port(A2x4h)
Address 24H
Bit(s) R/W Name Description
7 Fmmute Mute FM
6 Wsmute Mute Wave stream
5 SPK4 select four speaker mode(emulate Line in to Line out )
4 Rear2front exchange rear and front channels’s speaker out
3 Waveinl Digital Wave recording Left channel
2 Waveinr Digital Wave recording Right channel
1-0 Reserved
Address 25H
Bit(s) R/W Name Description
7 RAUXREN Recording source select R-Aux
6 RAUXLEN Recording source select L_Aux
5 VAUXRM R-AUX mute control
4 VAUXLM L-AUX mute control
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
3-1 VADMIC[2:0] Recording MIC volume control
0 MICGAINZ MIC gain control,default high disable
Address 26H
Bit(s) R/W Name Description
7-4 VAUXL[3:0] L-AUX volume control
3-0 VAUXR[3:0] R-AUX volume control
Address 27H
Bit(s) R/W Name Description
0 DMAUTO SB16 Low/High DMA Auto detect enabled ,When high.
1 Reserved
2 XGPBIO general purpose bi-direction pin, when high output tri-state
(default LOW)
3 Reserved
4 Reserved
5 XGPO1 general purpose output pin 1,this pin shared with XSPDIFO pin,
and enabled when index reg. F0_bit 0 programmed high.
6-7 Reserved
Mup401 PCI Port
Index address 40-4FH
FM PCI Port
Index address 50-5FH
Extension Index Register (access from SB compatible mixer port)
Index address F0H
Bit(s) R/W Name Description
7-5 VPHONE[2:0] Phone volume control
4 VPHOM Phone mute control
3 VSPKM PC-Speaker mute control,default high unmute
2 RLOOPREN Recording R-channel enable
1 RLOOPLEN Recording L-channel enable
0 VADMIC3 Micphone record boost, default low disable, high enable.
Index address F8-FFH
These 8 registers is used to programming M/N conunter by clock generator
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
Channel 0 Frame Register 1
Address 80H
Bit(s) R/W Name Description
31-0 W BASADDR0 Base address of channel 0.
R CURADDR0 Current address of channel 0.
Channel 0 Frame Register 2
Address 84H
Bit(s) R/W Name Description
31-16 W BASCNT0 Base count of samples at Codec.
15-0 W BASCNT0 Base count of samples at Bus Master.
31-16 R CURCNT0 Current count of samples at Cod e c.
15-0 R CURCNT0 Current count of samples at Bus Master.
Channel 1 Frame Register 1
Address 88H
Bit(s) R/W Name Description
31-0 W BASADDR1 Base address of channel 0.
R CURADDR1 Current address of channel 0.
Channel 1 Frame Register 2
Address 8CH
Bit(s) R/W Name Description
31-16 W BASCNT1 Base count of samples at Codec.
15-0 W BASCNT1 Base count of samples at Bus Master.
31-16 R CURCNT1 Current count of samples at Cod e c.
15-0 R CURCNT1 Current count of samples at Bus Master.
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
Legacy SB compatible mixer
Index D7 D6 D5 D4 D3 D2 D1 D0
0x00 Reserved
0x04 Wave volume left channel Wave volume right channel
0x0A Mic volume
0x22 Master volume left channel Master volume right channel
0x26 FM volume left channel FM volume right channel
0x28 Analog-CD volume left channel Analog-CD volume right channel
0x2E Line-in volume left channel Line-in volume right channel
0x30 Reserved
0x31 Reserved
0x32 Reserved
0x33 Reserved
0x34 Reserved
0x35 Reserved
0x36 Reserved
0x37 Reserved
0x38 Reserved
0x39 Reserved
0x3A Reserved
0x3B PC spk volume
Output muting controls 0x3C Line L Line R CD L CD R Mic
Recording left channel controls 0x3D FM L FM R Line L Line R CD L CD R Mic
Recording right channel controls 0x3E FM L FM R Line L Line R CD L CD R Mic
0x3F Reserved
0x40 Reserved
0x41 Reserved
0x42 Reserved
0x43 Reserved
0x44 Reserved
0x45 Reserved
0x46 Reserved
0x47 Reserved
IRQ channel (read only) 0x80
IRQ10 IRQ7 IRQ5 IRQ2(9)
16 bit DMA channel (read only) 8 bit DMA channel (read only) 0x81 DMA 7 DMA 5 DMA 3 DMA 1 DMA 0
Interrupt status (read only)
0x82
MPU-40
1 16bit
DMA 8bit
DMA
z Please do not write any values into reserved registers
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
1. Stereo
It is only one-dimensional, as sounds come from (left /right) the physical location of
speakers.
2. Surround (Stereo Expander )
It filters the existing stereo signal to make the sounds fill in the area around the speakers,
and in front of the listener. Sound sources appear to come from outside the physical
locations of the speakers.
3. Multi-Speaker Surround (Dolby Pro Logic or Digital AC-3)
It uses five speakers instead of two to surround the listener; hence, sound sources come
from five directions and create engaging audio experience. This surround sound effect,
however, has to be pre-recorded, and it dose not support interactive environment.
Audio Processing Technology
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
4. HRTF 3D Positional 3D (C-Media 3D)
Only this sound processing technology can be called real 3D manifestation, as 3D
usually refers to the three dimensions of X, Y and Z. This technology allows people to
pin-point the location of sound in the real world (up/down, left/right, front/back)using only
two speakers or a pair of headphones. This technology also supports interactive 3D
applications to get a real-time placement of sounds via API (application programming
interface) such as Microsoft DirectSound3DTM. We can also use this technology to
simulate Multi-speaker Surround with two physical speakers to deliver five “virtual"
speakers in the air, surrounding the listener and creating home theater sound
environment. This is the most economical and the easiest solution to people who would
like to get high performance surround sound but don’t want to spend money in adding
extra speakers.
A virtual
speaker
A physical
speaker
Audio Processing Technology
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
5. HRTF 3D Extension Positional (C-Media 3DX)
3D illusion exists because traditional 3D positional audio system assumes the user's
position as the sweet spot to design crosstalk-cancellation circuit; therefore, if the user
wants to have 3D positional audio effects, he can’t move his head or position out of sweet
spot. Another 3D illusion fails because half the population are compulsive
"head-turners" who will never get 3D audio from two speakers . To remedy this,
C-Media utilizes HRTF 3D extension technology (C3DX) to enhance traditional HRTF 3D
positional audio by substituting two-speaker system by four-speaker one. Therefore, at
least one or two speakers should be placed behind the listener's head to complement
the rear-side effect, thus creating compelling realistic sound. This technology greatly
improves HRTF 3D positional audio quality, and successfully eliminates the sweet spot
limitation. Users can enjoy the real 3D audio gaming effects, and don't have to worry
about the environmental confinement any more.
A virtual
speaker A physical
speaker
Audio Processing Technology
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
C3D HRTF Positional Audio Technology
C3D technology uses an audio filter called Head Related Transfer Functions (HRTFs), which
is licensed from CRL®(Central Research Lab). The basic concept of C3D is: since we can
hear sound three dimensionally in the real world using our two ears, it must be possible to
regenerate the same sound effect from two loud speakers.
What is HRTF ?
HRTF (Head Related Transfer Functions) is a set of audio filters which can vary locations of
sound effects (spatial hearing cues) in three-dimension measured from the listener's
eardrum.
People can use this technology and special digital signal processing to re-create spatial
hearing cues, so as to makes the ears hear a realistic and three-dimensional sounds coming
from a pairs of loud speakers or headphones.
There are several listening cues which allow people to hear
sounds three-dimensionally :
(I). Spatial Hearing : Primary 3D-cues
1. IAD
The head shadowing effect creates differences in the amplitudes of the sound signals
arriving at each ear from the source. The effects of diffraction are most noticeable in
the range between about 700 Hz to 8 KHz, where the A and S functions periodically
converge and diverge gently. This Inter-aural Amplitude difference (IAD) is one of the
primary 3D sound cues.
HRTF 3D Positional Audio Technology White-Paper
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
2. ITD
In addition to IAD, there is also a time-of-arrival difference between the left and right
ears(unless the sound source is in one of the pole positions, such as directly in front,
behind, above and below): this is known as the Inter-aural Time Delay (ITD).
HRTF 3D Positional Audio Technology White-Paper
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
3. Pinna Effects
It has been presumed by several researchers that the convolutions of the pinna create
the spectral features which constitute the 'height' cues. In practical experiments by
Gardner, in which different parts of the pinna were occluded, and then the ability of a
number of subjects to identify sound source positions at different heights was tested, it
was shown that the different features all contributed by different amounts. For example,
if the fossa is excluded, then height localization capability is impaired, but not totally
extinguished. It would be reasonable to conclude that it is the combined effect of the
pinna convolutions which create the various localization cues, and it is not valid - or
logical - to attempt to assign particular spatial capabilities with individual physical
features.
(II). Spatial Hearing : Secondary 3D-cues (shoulder & local reflections)
In addition to the 'primary' 3D sound cues (IAD, ITD and pinna effects), there are several
additional cues which do contribute to the localization capability; these will be referred to
here as 'secondary' cues, and include shoulder/torso reflections, local room reflections, and
psychological cues.
1. Shoulder / Torso reflections
The presence of a torso attached to an artificial head has the effect of increasing the
pressure in the vicinity of the ear up to frequencies of around 2 kHz. The effect is greater
for frontal sources than lateral ones. In experience, the presence of the torso does not
appear to contribute much to spatial accuracy. However, shoulders are located very close
to the ears, and their effect is greater, this time, in respect of
HRTF 3D Positional Audio Technology White-Paper
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
lateral sounds. If one listens to an artificial head first without - and then with - shoulder
fitments, then it is clear that the shoulders do contribute to spatial effects in certain positions.
The shoulders provide a strong reflection from lateral sources, with a short path-length of
around 10 cm between direct sound and reflection. The effects are most important for
side-positioned sources, especially for "height" effects, where the shoulders tend to mask
sources which move below about 30 degree depression.
2. Local, Room Reflections
In simulations, it is clear that the incorporation of first-order simulated room reflections can
help in the creation of sound images which have a "solid" nature. However, the effects - if
accurately simulated - are relatively slight. Experience has shown that it is primarily the
quality of the HRTFs themselves which determine the quality and solidity of the sound image.
The further addition of second-order reflections does not help significantly, because in reality,
there is a great number of reflections in the average room. A method which does help to
recreate the acoustic experience of a room, however, is to use approximate simulations of
lateral reverb, using either 2 or 4 laterally placed "virtual" sources at, say, +-70 degrees and
80 degrees azimuth.
• The quality of the sound image relates to the HRTFs used.
• The quality of the room image relates to addition of reflections and reverb.
3. Psychological Cues
There are clearly psychological cues present in everyday life which work together with the
audio cues to tell us about the world around us. For example, if you hear the sound of a
helicopter flying, you expect it to be up in the air, and not downwards. If a dog is barking
nearby, you would expect it to be downwards.
HRTF 3D Positional Audio Technology White-Paper
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
How to listen to C3D sound correctly and properly?
1. Use Headphones to Have Much Better Effect
When you use headphones in listening, there will be less interference such as outside voices
or room reflections comparing to using speakers.
2. Choose Correct Output Devices
Choose the correct output devices in the options of demo program in accordance with what
listening devices you want to listen to. Listening through speakers must be proceeded by
crosstalk-cancellation, so if you choose the wrong output devices, there won’t be any 3D
positional audio effect.
HRTF 3D Positional Audio Technology White-Paper
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
3. Position of Speakers
If you listen from speakers, please do not reverse the left and right speakers, which should
be put in equal distance from the listener. That is, the listener, the left, and the right
speaker must be in the topmost of a right triangle. The position of the listener is called the
“sweet spot”. In addition, the height of the listener’s ears must be equal to that of the
speakers.
4. Turn Surround Sound Functions off
When the surround sound effect is enabled, it will cause confusion with C3D sound, and
make positional sound effect invalid.
HRTF 3D Positional Audio Technology White-Paper
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
Audio Rack Panel
Audio Rack Panel
Two Speakers System :
Four Speakers System :
4 Speakers
system Enable
Line-In becomes
Rear Speakers Output
C-MEDIA ELECTRONICS INC. Tel:886-2-87731100 Fax:886-2-87732211 URL : www.cmedia.com.tw
Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI-SX AUDIO Specificatio n
Ver. 1.2
CMI8738 PCI Audio Adapter Layout Notes
1. The wires of analog circuits(chip pin64-80) must be wider than 12mil.
2. The whole PCB grounding should be well-organized(The ground must be placed
as much as possible. Also, the ground of both the component and the solder
sides should be drilled as much as possible.).
3. The grounding under CMI8738 should be well-organiz ed as mentioned above.
4. The regulator(78L05) must be placed near the chip as much as possible.
5. The chip and the circuits need independent power supply regulators to prevent
insufficient currents.
