Sound Blaster 16

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The Sound Blaster series is a family of sound cards made by Creative. For many years they were the standard audio cards on IBM PC's.

Contents

Introduction

The Sound Blaster 16 is the successor to the Sound Blaster Pro audio card found in many older computers. It was first brought out in 1992. The main improvement over the Pro is its 16-bit digital audio sampling (hence the name). Most SB16 cards are PCI compatible, as Creative made this improvement shortly after releasing the card, upgrading from ISA.

Digital Signal Processor

The DSP built into the Sound Blaster 16 supports playing and recording audio in 8-bit and 16-bit PCM encoded samples, along with playing several other formats (ADPCM, etc.). The base I/O register address can be found using the PCI bus for PCI models, or by detecting the presence of an older ISA Sound Blaster by issuing a Get Version command to one of several common I/O port addresses (0x220, 0x240, etc.) and waiting for a response.

Port Description
0x224 DSP Mixer port
0x225 DSP Mixer data port
0x226 DSP Reset
0x22A DSP Read
0x22C DSP Write
0x22E DSP Read Status (Read this port to acknowledge 8-bit interrupt)
0x22F DSP 16-bit Interrupt Acknowledge (Read this port to acknowledge 16-bit interrupt) (DSP Version 4.0+ Only)
Command for DSP Write Description Output/input for command
0x40 Set time constant 8 bit value
0x41 Set Output Sample Rate high bit/low bit
0xD1 Turn speaker on
0xD3 Turn speaker off
0xD0 Stop playing 8 bit channel
0xD4 Resume playback of 8 bit channel
0xD5 Stop playing 16 bit channel
0xD6 Resume playback of 16 bit channel
0xE1 Get DSP version major version/minor version
Command for Mixer port Description Mixer data port
0x22 Master volume 0xLR L=left volume R=right volume min=0x0 max=0xF (default value is 0xCC or 0x11)
0x80 Set IRQ See below

There are two modes for transfering data. First is single mode - data from buffer are played, interrupt is fired and playing is stopped. It make lower quality of sound. Second is auto mode - data from buffer are playing forever and interrupt is fired after play buffer. You should use interrupt for re-filling buffer.

Operations

Reseting DSP (detecting DSP)

  1. Send 1 to DSP reset port
  2. Wait 3 microseconds
  3. Send 0 to DSP reset port
  4. Now should be in DSP read port 0xAA.

Some SB-compatible cards returned 0xAA on first check but on second check they reported their specific version.

Setting IRQ

  1. Send 0x80 to Mixer port
  2. Send value of your IRQ to Mixer data port

0x01=IRQ 2 0x02=IRQ 5 0x04=IRQ 7 0x08=IRQ 10 Usually is used IRQ 5. You can read this port too for get actual IRQ.

Programming DMA

You can get more info about DMA here.

Programming 8 bit transfers throught channel 1 (channel number is 1):

  1. Disable channel by writing to port 0x0A value 0x05 (channel number + 0x04)
  2. Write value to flip-flop port 0x0C (any value e.g. 1)
  3. Send transfer mode to 0x0B (0x48 for single mode/0x58 for auto mode + channel number)
  4. Send page number to 0x83(page port of channel 1) For example if you have sound data at 0x100450, page is 0x10.
  5. Send low bits of position to port 0x02(addr. port of channel 1) For example(see above) is 0x50.
  6. Send high bits of position to port 0x02(addr. port of channel 1) For example(see above) is 0x04.
  7. Send low bits of length of data to port 0x03(count port of channel 1) For example if is length 0x0FFF, send 0xFF
  8. Send high bits of length of data to port 0x03(count port of channel 1) For example if is length 0x0FFF, send 0x0F
  9. Enable channel by writing channel number to port 0x0A

Programming 16 bit transfers throught channel 5 (channel number is 1 too):

  1. Disable channel by writing to port 0xD4 value 0x05 (channel number + 0x04)
  2. Write value to flip-flop port 0xD8 (any value e.g. 1)
  3. Send transfer mode to 0xD6 (0x48 for single mode/0x58 for auto mode + channel number)
  4. Send page number to 0x8B(page port of channel 5) For example if you have sound data at 0x100450, page is 0x10.
  5. Send low bits of position to port 0xC4(addr. port of channel 5) For example(see above) is 0x50.
  6. Send high bits of position to port 0xC4(pos. port of channel 5) For example(see above) is 0x04.
  7. Send low bits of length of data to port 0xC6(count port of channel 5) For example if is length 0x0FFF, send 0xFF
  8. Send high bits of length of data to port 0xC6(count port of channel 5) For example if is length 0x0FFF, send 0x0F
  9. Enable channel by writing channel number to port 0xD4

Writing transfer mode to DSP

Usually values are 0xB0 for 16 bit playing sound or 0xC0 for 8 bit playing sound.

Bit 7-4 Bit 3 Bit 2 Bit 1 Bit 0
0xB=16 bit transfer 0xC=8 bit transfer 0=playing sound 1=recording sound 0 0=FIFO off 1=FIFO on 0

Writing type of sound data to DSP

You must write type of sound data after write transfer mode.

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
0 0 0=mono 1=stereo 0=unsigned 1=signed 0 0 0 0

Playing sound

  1. Reset DSP
  2. Load sound data to memory
  3. Set master volume
  4. Turn speaker on
  5. Program ISA DMA to transfer
  6. Set time constant. Notice that the Sound Blaster 16 is able to use sample rates instead of time constants using command 0x41 instead of 0x40.
    You can calculate the time constant like this: Time constant = 65536 - (256000000 / (channels * sampling rate))
  7. Set output sample rate
  8. Write transfer mode to DSP
  9. Write type of sound data
  10. Write data length to DSP(Low byte/High byte) (You must calculate LENGTH-1 e.g. if is your real length 0x0FFF, you must send 0xFE and 0x0F)

Code

  %macro OUTB 2
    mov dx, %1
    mov al, %2
    out dx, al
  %endmacro
 
  %macro INB 1
    mov dx, %1
    in al, dx
  %endmacro
 
 
  ;SOUND BLASTER 16 driver in real mode
 
  ;reset sound blaster
  OUTB 0x226, 1 ;reset port
  mov ah, 86h
  mov cx, 0x0000
  mov dx, 0xFFFF
  int 15h ;wait
  OUTB 0x226, 0 ;reset port
 
  ;turn speaker on
  OUTB 0x22C, 0xD1
 
  ;DMA channel 1
  OUTB 0x0A, 5 ;disable channel 1 (number of channel + 0x04)
  OUTB 0x0C, 1 ;flip flop
  OUTB 0x0B, 0x49 ;transfer mode
  OUTB 0x83, 0x01 ;PAGE TRANSFER (EXAMPLE POSITION IN MEMORY 0x[01]0F04) - SET THIS VALUE FOR YOU
  OUTB 0x02, 0x04 ;POSITION LOW BIT (EXAMPLE POSITION IN MEMORY 0x010F[04]) - SET THIS VALUE FOR YOU
  OUTB 0x02, 0x0F ;POSITON HIGH BIT (EXAMPLE POSITION IN MEMORY 0x01[0F]04) - SET THIS VALUE FOR YOU
  OUTB 0x03, 0xFF ;COUNT LOW BIT (EXAMPLE 0x0FFF) - SET THIS VALUE FOR YOU
  OUTB 0x03, 0x0F ;COUNT HIGH BIT (EXAMPLE 0x0FFF) - SET THIS VALUE FOR YOU
  OUTB 0x0A, 1 ;enable channel 1
 
  ;program sound blaster 16
  OUTB 0x22C, 0x40 ;set time constant
  OUTB 0x22C, 165 ;10989 Hz
  OUTB 0x22C, 0xC0 ;8 bit sound
  OUTB 0x22C, 0x00 ;mono and unsigned sound data
  OUTB 0x22C, 0xFE ;COUNT LOW BIT - COUNT LENGTH-1 (EXAMPLE 0x0FFF SO 0x0FFE) - SET THIS VALUE FOR YOU
  OUTB 0x22C, 0x0F ;COUNT HIGH BIT - COUNT LENGTH-1 (EXAMPLE 0x0FFF SO 0x0FFE) - SET THIS VALUE FOR YOU
 
  ;now transfer start - don't forget to handle irq

QEMU support

QEMU is one of the few hypervisors/emulators that support this sound card. To run QEMU with Sound Blaster 16 emulation, use the -soundhw sb16 option.

Warning: recent versions of QEMU (>= 4.0) have a broken support for this sound card. See bug: [1]. Briefly, when QEMU's GTK UI is used and audio is playing, you'll experience the QEMU window freezing. In addition, there will be flickering in the audio as well.

Workarounds

  1. Use an older version of QEMU. With QEMU 2.11 the problem simply does not exist.
  2. Use virt-manager which connects to QEMU using Spice. The problem does not exist in this case because QEMU's GTK UI is not used. BUT, configuring QEMU to emulate Sound Blaster 16 through virt-manager requires some tricky settings:
    1. Add any sound card to the VM
    2. In virt-manager's Edit -> Preferences menu check the "Enable XML editing" box.
    3. Open VM's hardware and after selecting the sound card, click on the XML tab and replace its contents with:
      <sound model="sb16"/>
  3. Run the OS using QEMU's -curses option or use QEMU's -kernel and -nographic (serial console): in this case, there will be no "freeze", but there still be some flickering in the audio.

See Also

External Links

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