Sound Blaster 16
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.
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.
To play audio, the ISA DMA controller must be programmed, then the DSP must be issued a Set Output Sample Rate command, and a Play command that includes the format of the audio (mono/stereo, signed, etc.) and a sample count.
| Register | Description |
|---|---|
| 0x04 | Mixer Port (Set to 0x82 for Interrupt Status) |
| 0x05 | Mixer Data (Read to get Interrupt Status) |
| 0x0a | DSP Read |
| 0x0c | DSP Write (Read this port for Write Status) |
| 0x0e | DSP Read Status (Read this port to acknowledge 8-bit interrupt) |
| 0x0f | 16-bit Interrupt Acknowledge (Read this port to acknowledge 16-bit interrupt) (DSP Version 4.0+ Only) |
| Command | Description |
|---|---|
| 0x41 | Set Output Sample Rate |
| 0xa6 | Play PCM (Auto Initialize DMA, FIFO Enabled) |
| 0xd9 | Stop PCM (Auto Initialize DMA) |
| 0xe1 | Get DSP Version |
When the samples have been played, an interrupt will be fired, and the OS/Driver will have the chance to refill the buffer, or to issue a Stop command.
Because you only have a single DMA buffer to transfer data, it is recommended that you issue the Play PCM command with a sample count of half of the data buffer. This will fire an interrupt when the buffer is half played, allowing you to refill the segment that was just played, while the DSP continues playing the other half, and so on.