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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI AUDIO Specification
Preliminary Ver 1.3
1
Ver. 1.3
CMI-8738/PCI C3DX
PCI-Based HRTF 3D Extension Positional Audio Chip
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. Above all CMI8738 supports PCtel®
HSP56 (1789) interface.
Being compatible with A3D™ and DirectSound™ 3D,
CMI8738 meets PC98® requirements, and supports professional
digital audio interface such as 24-bit SPDIF IN (0.5V ~ 5V)and
OUT(44.1K and 48K format).
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 (CRL® also licensed its audio technology to YAMAHA®,
ESS®, and other well-known sound chip makers).
Features
HRTF-based 3D positional audio,
supporting DirectSound™ 3D and A3D™
interface
Supports rear side speakers, C3DX
positional audio in 4 CH speaker mode
Legacy audio SB16™ compatible
DLS-based wavetable music synthesizer,
supports DirectMusic™
Professional digital audio interface
supporting 24-bit SPDIF IN and OUT (44.1K
and 48K format)
Built-in 32ohm Earphone buffer
Built-in PCtel® HSP56 Modem™ interface
Drivers support AC3® 5.1CH interface.
MPU-401 port
Dual game port
16-bit full duplex CODEC
4 CH 16-bit DAC
32-bit PCI bus master
External E²PROM interface
Single chip design, +5V, 128 pins QFP
HSP56 Modem interface
CMI-8738/PCI Block Diagram
MPU 401 and
GAME port
DMA engine
IRQ control
Legacy audio
SB16™emulator
SPDIF IN and
OUT
16-bit CODEC
LINE
OUT
Earphone
buffer
3D
Surround
MIC AMP
MIC IN
Rear
L/R
LINE / CD /
AUX / PCPSK
IN
Analog Mixer
Music Synthesizer
HRTF DSP engine
PCI BUS
PCI interface
14.
3
1
8
Mhz
PLL and
timing circuit
Ver. 1.3
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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI AUDIO Specification
PINOUT
PINOUT
XO
U1
CMI8738B
XAF ER ST
103
XSC LK
104
XHSPFS
105
XHSPSDI
106
XHSPSDO
107
XAF EMC LK
108
XBI O3
109
XBI O2
110
XBI O1
111
XBI O0
112
XHNDSET
113
XMDSEL
114
VDD
115
GND
116
XI N TA
117
XI N TB
118
XPR ST
119
XC LK33
120
XGN T
121
XR EQ
122
XADOUTL 64
XVR EF 63
XINTVREF 62
AVDD 61
AGND 60
XAFEPD 59
XMOU T 58
XMI N 57
XOU T 56
XI N 55
VDD 54
GND 53
XA0 52
XA1 51
XA2 50
XA3 49
XA4 48
XA5 47
GND 46
VDD 45
XA27 2
GND 3
VDD 4
XA26 5
XA25 6
XA24 7
XCBE3 8
XIDSEL 9
VDD 10
GND 11
XA23 12
XA22 13
XA21 14
XA20 15
XA19 16
GND 17
VDD 18
XA18 19
A17 20
XA16 21
XCBE2 22
XF R AME 23
XI R D Y 24
XTR D Y 25
XDEVSEL 26
VDD 27
GND 28
XSTO P 29
XPAR 30
XCBE1 31
XR I N G
101 VDDM
100 DGND
99 XSPDIFO
98 XGD 7
97 XGD 6
96 XGD 5
95 XGD 4
94 XGD 3
93 XGD 2
92 XGD 1
91 XGD 0
90 XR XD
89 XTXD
88 XGPBIO
87 XSPDIFI
86 XMBCSZ
85 XEECS
84 VDD5V
83 AGND
82 AVDD
81 XMICIN
80 XPCSPKIN
79 XAU XR
78 XAU XL
77 XLN R
76 XLN L
75 XREARR
74 XREARL
73 XC D R
72 XA15 32
XA14 33
XA13 34
XA12 35
GND 36
VDD 37
XA11 38
XA10 39
XA9 40
XA8 41
XCBE0 42
XA7 43
XA6 44
XA29
128 XA30
127 XA31
126 GND
125 VDD
124 XPME
123
XA28 1
XADOUTR
65
XADCHL
66
XADCHR
67
XLF I LT
68
XR F I L T
69
XCDGND
70
XC D L
71
FFHOOK
102
CMI8738/PCI C3DX AUDIO CHIP
QFP 128 PINS
2
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CMI-8738/PCI AUDIO Specification
PIN DESCRIPTION
3
Ver. 1.3
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 , active-low.
XINTB 118 O Modem Interrupt request,active-low
XPRST 119 I Reset
XCLK33 120 I PCI bus clock.
XGNT 121 I Bus master grant, active-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 decoded the
address of the current transaction
as its own chip select range.
XSTOP 29 I/O Stop transaction, active-low. The
target device request 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 3,11,17,28,36,46,53,116,125 GND Digital and PCI I/O ground
XIN 55 I 14.318Mhz crystal, 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
XSPDIFO 98 O 44.1kHZ SPDIF output
XSPDIFI 86 I* 44.1kHZ SPDIF input
XSCLK 104 O MODEM DAA serial clock
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
Ver. 1.3
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CMI-8738/PCI AUDIO Specification
PIN DESCRIPTION
ANALOG PIN DESCRIPTION
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
XINTVREF 62 AI Reference Voltage
XVREF 63 AI Reference Voltage (no use, left it
floating)
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
XMDSEL 114 I Modes chip select (high:enable)
XGPBIO 87 O General purpose I/O pin
(0=disabled, 1=enabled)
XRING 101 I Ring detection input
XOFFHOOK 102 O Off-hook control output
XAFERST 103 O Reset signal for MODEM DAA
XHSPFS 105 O MODEM DAA frame SYNC
XHSPSDI 106 I MODEM DAA data input
XHSPSDO 107 O MODEM DAA data output
XAFEMCLK 108 O MODEM DAA master clock
XHNDSET 113 O Reserved
XAFEPD 59 O Reserved
XMOUT 58 O MODEM crystal output (18.432MHz)
XMIN 57 I MODEM crystal input
XMBCSZ 85 I Audio chip select (low:enable)
4
Ver. 1.3
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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI AUDIO Specification
POWER ON CONFIGURATION PIN
Name Number Definition
XTXD 88 When pull-down select add-on mode,
default pull-high motherboard.
XAFEPD 59 When pull-down enable #INTB share with #INTA,
default high disabled.
XHNDSET 113 When pull-down enable external 18.432Mhz x'tal to HSP module,
default pull-high enable internal 24.576Mhz to HSP module.
XBIO0 112 When pull-down select CLKGEN ref. clock to external
24.576Mhz x'tal. default pull-high select 14.318Mhz
5
Ver. 1.3
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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI AUDIO Specification
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
SPDIF IN input high voltage VIH1 2.6 V
SPDIF IN input low voltage VIL1 2.4 V
SPDIF output high voltage VOH1 VDD V
SPDIF output low voltage VOL1 VSS 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 %
SPDIF IN/OUT S/N ratio 120 db
SPDIF IN/OUT THD 0 %
Microphone input level 20 200 mv
Microphone booster 20 db
6
CMI-8738/PCI AUDIO Specification
Configuration Space
7
Ver. 1.3
CMI8738 PCI Configuration Spaces(Audio)
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
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CMI-8738/PCI AUDIO Specification
Configuration
8
Ver. 1.3
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
CMI8738 Configuration Spaces(Modem)
00h 13F6: (Vender ID) read only
02h 0211: (Device ID) read only
04h Command (State after #RST all is "0")
0 (bit 9) Fast back-to-back enable (read only)
0 (bit 8) #SERR enable (Read only)
0 (bit 7) Wait cycle control (read only)
0 (bit 6) Parity error response (read only)
0 (bit 5) VGA palette snoop (read only)
0 (bit 4) Memory write and invalidate enable (read only)
0 (bit 3) Special cycles (read only)
0 (bit 2) Bus master (read only)
1 (bit 1) Memory space (R/W)
0 (bit 0) I/O space (read only)
06h Status
B0 (bit 15) Detected Parity Error
B0 (bit 14) Signaled System Error
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Ver. 1.3
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 AUDIO Specification
B0 (bit 13) Received Master Abort
B0 (bit 12) Received Target Abort
B0 (bit 11) Signaled Target Abort
B01 (bits 10-9) DEVSEL timing 00-fast, 01-medium, 10-slow
B0 (bit 8) Data parity Error Detected
B0 (bit 7) Fast Back-to-Back Capable
B0 (bit 6) UDF Supported
B0 (bit 5) 0-33MHz, 1-66MHz Capable
B00000 (bits 4-0) Reserved
08h X10: Revision ID
09h X078000: Communication device (Modem)
0Ch X00: Cache Line Size
0Dh X00: latency Timer
oEh X80: Header Type (Multifunction device)
oFh X00: BIST
10h Xbbbbb000: Allocate 4K memory space.
14h X00000000: not used - Second Base Address register
18h X00000000: not used - Third Base Address register
1Ch X00000000: not used- Four Base Address register
20h X00000000: not used- Fifth Base Address register
24h X00000000: not used- Sixth Base Address register
28h X00000000: Card bus CIS Pointer
2Ch X13f6: Sub-System Vender ID (Value can be replaced after reset.) (R/W)
2Eh X0211: Sub-System ID (Value can be replaced after reset) (R/W)
*Refer to the Audio PCI registers bit-13 of address (18-1B) for how to replace.
30h X00000000: Expansion ROM Base Address
34h X00000040: pointer to the power-saving registers. (Read only)
38h X00000000: Reserved
3Ch X00: Interrupt Line (R/W)
3Dh Interrupt Pin(X01 share interrupt/X02 not share interrupt with Audio)
*Select from the power on pin configuration
3Eh X00: Min Grant(not used)
3Fh X00: max Latency(not used)
40h XEC4A0001(read only)
9
Ver. 1.3
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CMI-8738/PCI AUDIO Specification
44h-47h
B0-B1: PMST (R/W) (11)
B7-B2: all 0 (read only)
B8: PMEEN (R/W) (Sticky bit)
B12-B9: DSEL (R/W) 0000
B14-B13: all 0 (read only)
B15: PMESTS (Sticky bit)
CMI-8738/PCI AUDIO Specification
PCI register
Ver. 1.3
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
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Ver. 1.3
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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI AUDIO Specification
1 0 1 16 K
1 1 0 32 K
1 1 1 48 K
9 SPDF_1 SPDIF IN/OUT at Channel B at 44.1K double-words/sec.
8 SPDF_0 SPDIF OUT only at Channel A at 44.1K double-words/sec.
7 SPDFLOOP external SPDIF/IN loopback to external SPDIF/OUT .
6 SPDO2DAC SPDIF/OUT can be heard from internal DAC.
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 disabled 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”
23-22 SWTCLK[1:0] In real mode, switch CLOCK Generator output to
XSPDIF/out.
0X maintain original spdif/out bit stream to XSPDIF/out.
10 16.9344MHZ to I/O XSPDIFO
11 24.576MHZ to I/O XSPDIFO
21 Reserved
20 AC3EN When set 1,it will generate AC3 enable bit on spdif/out
FRAMA #1 bit 30 ( channel status bit)
Ver. 1.3
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CMI-8738/PCI AUDIO Specification
19 SELSPDIFI2 When set 1,internal spdif/in will switch to secondary
SPDIF/IN I/O(XHNDSET)
18 FMOFFSET2 When set 1 and Reg. 24H bit7 ‘FMmute=1’,FM PCM will be
forced to DC value 0002H.
17 SPD24SEL When set 1 and SPD32SEL=1,SPDIF/out transmit 24bit
PCM data,PCM data in system format only valid in 24 least significant Bits D[23:0] ,bits D[31:24]
don’t care.
16 INVSPDIFI Inverse spdif/in data,function for compatible to different
CD-ROM .
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.
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
Ver. 1.3
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CMI-8738/PCI AUDIO Specification
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
1 Interrupt pending
30-28 Reserved
27 R VCO
26 R MCBint Abort conditions occur during PCI Bus Target/Master
Access.
0 No interrupt
0 Interrupt 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 Interrupt for updating Low Channel TDMA position.
0 No interrupt
1 Interrupt pending
14 R HTDMAINT Interrupt for updation High Channel TDMA 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.
Ver. 1.3
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CMI-8738/PCI AUDIO Specification
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 Interrupt 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
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 ENSPDOUT enable XSPDIF/OUT to I/O Interface
22 SPDCOPYRHT SPDIF IN/OUT CopyRight status bit
21 DAC2SPDO enable Wave+FM+MIDI to SPDIF/OUT interface
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
Ver. 1.3
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CMI-8738/PCI AUDIO Specification
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 SPDO5V SPDIF-out level setting
24 W / SPDIF48K ; R / SPATUS48K ;
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 SPD32SEL when high, support 32bits SPDIF format ,low 16bits
20 SPDFLOOPI internal SPDIF/OUT loopback to internal SPDIF/IN, for
loopback testing
19 FM_EN Legacy FM enabled.
18 Reserved
17 Reserved
16 VIDWPDSB Sub ID write protect disabled. (default 0)
15 SPDF_AC97 0: SPDIF/OUT 44.1K 1:SPDIF/OUT 48K(share with
AC97 transfer)
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.
11-9 Mmode[2:0] Modem DAA interface mode selection,default 000
000 Modem in Local DAA interface mode
001 Modem in AC97_LINK mode
Ver. 1.3
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CMI-8738/PCI AUDIO Specification
010 Modem in parallel CM_LINK mode (external modem
bridge supported)
1XX Modem in serial CM_LINK mode (external modem
bridge supported)
8 Reserved
7 FLINKON force Link detection on when in CM_LINK mode,default 0
6 FLINKOFF force Link detection off when in CM_LINK mode,default 0
5 Reserved
4 MIDSMP Enable 1/2 interpolation at the 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.
Mixer Control / Device Configure Register (can be accessed only by BYTE
Ver. 1.3
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CMI-8738/PCI AUDIO Specification
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 X3DEN 3D surround enable.
0 Cdplay SPDIF/IN PCM to DAC enable
Address 25H
Bit(s) R/W Name Description
7 RAUXREN Recording source select R-Aux
6 RAUXLEN Recording source select L_Aux
Ver. 1.3
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CMI-8738/PCI AUDIO Specification
5 VAUXRM R-AUX mute control
4 VAUXLM L-AUX mute control
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 SPDVALID SPDIF/IN valid bit detect enabled, When high.
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.
Ver. 1.3
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CMI-8738/PCI AUDIO Specification
Index address F8-FFH
These 8 registers is used to programming M/N conunter by clock generator
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 Codec.
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 Codec.
15-0 R CURCNT1 Current count of samples at Bus Master.
Ver. 1.3
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CMI-8738/PCI AUDIO Specification
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
Please do not write any values into reserved registers
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CMI-8738/PCI AUDIO Specification
SPDIF Test Report
Ver. 1.3
CMI8738 SPDIF IN/OUT Test Report
CMI8738 SPDIF-out 03/04/99 12:19:31Frequency, Distortion Noise Response
Color Line Style Thick Data Axis
Green Solid 1 Fasttest.Ch.1 Am pl Left
Yellow Solid 1 Fasttest.Ch.2 Ampl Left
-160
-20
-140
-120
-100
-80
-60
-40
d
B
F
S
20 10k50 100 200 500 1k 2k 5k
Hz
CMI8738 SPDIF-in 03/04/99 14:11:15Frequency, Distortion Noise Response
Color Line Style Thick Data Axis
Green Solid 1 Fasttest.Ch.1 Am pl Left
Yellow Solid 1 Fasttest.Ch.2 Ampl Left
-160
-20
-140
-120
-100
-80
-60
-40
d
B
F
S
20 10k50 100 200 500 1k 2k 5k
Hz
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CMI-8738/PCI AUDIO Specification
SPDIF Test Report
Ver. 1.3
CMI8738 SPDIF-through 03/04/99 12:36:04Frequency, Distortion Noise Response
Color Line Style Thick Data Axis
Green Solid 1 Fasttest.Ch.1 Am pl Left
Yellow Solid 1 Fasttest.Ch.2 Ampl Left
-160
-20
-140
-120
-100
-80
-60
-40
d
B
F
S
20 10k50 100 200 500 1k 2k 5k
Hz
1. SPDIF OUT (playback) > 120db
2. SPDIF IN (recording ) > 120db
3. SPDIF through mode (bypass) > 120db
* This report is generated by Audio Precision® System II using multi-tone mode.
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CMI-8738/PCI AUDIO Specification
Audio Processing Technology
Ver. 1.3
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.
Ver. 1.3
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CMI-8738/PCI AUDIO Specification
Audio Processing Technology
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
physical
speaker A virtual
speaker
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CMI-8738/PCI AUDIO Specification
Audio Processing Technology
Ver. 1.3
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
physical
speaker
A virtual
speaker
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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI AUDIO Specification
HRTF 3D Positional Audio Technology White-Paper
Ver. 1.3
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.
Ver. 1.3
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CMI-8738/PCI AUDIO Specification
HRTF 3D Positional Audio Technology White-Paper
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).
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CMI-8738/PCI AUDIO Specification
HRTF 3D Positional Audio Technology White-Paper
Ver. 1.3
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
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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI AUDIO Specification
HRTF 3D Positional Audio Technology White-Paper
Ver. 1.3
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.
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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI AUDIO Specification
HRTF 3D Positional Audio Technology White-Paper
Ver. 1.3
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.
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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI AUDIO Specification
HRTF 3D Positional Audio Technology White-Paper
Ver. 1.3
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.
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CMI-8738/PCI AUDIO Specification
Audio Rack Panel
Ver. 1.3
Audio Rack Panel
Line-In becomes
Rear Speakers Output
4 Speakers
system Enable
Four Speakers System :
Two Speakers System :
Ver. 1.3
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Products and company names mentioned here are the trademarks of their respective owners.
CMI-8738/PCI AUDIO Specification
CMI8738 PCI Audio Adapter Layout Notes
1. The wires of analog circuits(chip pin64-80) must be wider than 12mil.
2. Placing digital signals such as SPDIF IN/OUT(pin86, 98) and
TXD/RXD(pin88,89) near the analog signals should be avoided. However,
if these signals have to be adjacent, please place ground between these
digital and analog signal wires to isolate noises.
3. 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.).
4. The grounding under CMI8738 should be well-organized as mentioned
above.
5. The regulator(78L05) must be placed near the chip as much as possible.
6. The chip and the circuits need independent power supply regulators to
prevent insufficient currents.
Ver. 1.3
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CMI-8738/PCI AUDIO Specification
Revision release note:
V1.1 12/17/2001
1. Add register listing.
V1.2 01/17/2003
2. Add Pin62 XINTREF description.
