289 lines
9.2 KiB
Plaintext
289 lines
9.2 KiB
Plaintext
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Programming the Sound Blaster ADC/DAC:
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2x6h DSP Reset Port Write Only
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2xAh DSP Read Data Port Read Only
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2xCh DSP Write Data or Command Write
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2xCh DSP Write Buffer Status (bit 7) Read
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2xEh DSP Data Available Status Bit 7) Read Only
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x = 1,2,3,4,5,6 for the Sound Blaster <= 1.5
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x = 1,2,3,4,5,6 for the Sound Blaster Micro Channel Version
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x = 2,4 for the Sound Blaster 2.0
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x = 2,4 for the Sound Blaster Pro
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The DSP: -----------------------------------------------------------------------
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Due to the different mode and the hardware performance of different audio
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cards, the maximum sampling rate is different.
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Input (ADC):
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Sound Blaster (<=1.5) Mono/Normal mode: 8-bit only 4KHz to 13KHz
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Sound Blaster (2.0) Mono/Normal mode: 8-bit only 4KHz to 13KHz
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Mono/High Speed mode: 8-bit only 13KHz to 15KHz
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Sound Blaster Pro Mono/Normal mode: 8-bit only 4KHz to 23KHz
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Mono/High Speed mode: 8-bit only 23KHz to 44.1KHz
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Output (DAC):
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Sound Blaster (<=1.5) Mono/Normal mode: 8-bit only 4KHz to 23KHz
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Sound Blaster (2.0) Mono/Normal mode: 8-bit only 4KHz to 23KHz
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Mono/High Speed mode: 8-bit only 23KHz to 44.1KHz
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Sound Blaster Pro Mono/Normal mode: 8-bit only 4KHz to 23KHz
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Mono/High Speed mode: 8-bit only 23KHz to 44.1KHz
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Some DSP Commands:
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10h Direct mode 8-bit DAC (single byte data transfer)
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14h DMA mode 8-bit DAC
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20h Direct mode 8-bit ADC (single byte data transfer)
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24h DMA mode 8-bit ADC
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40h Set Time Constant
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48h Set Block Size
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91h High Speed DMA mode 8-bit DAC
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99h High Speed DMA mode 8-bit ADC
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D1h Turn on Speaker
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D3h Turn off Speaker
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D0h Halt DMA in progress
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D4h Continue DMA
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E1h Get DSP version (read major ver then minor)
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To reset the DSP:
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1. Write a 01h to port 2x6h
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2. Wait for 3 microseconds
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3. Write a 00h to port 2x6h
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4. Read port 2xAh until a 0AAh is read (see below for how to read from 2xAh)
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If there is no 0AAh after about 100 reads, abort and declare that there is no
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Sound Blaster present (or error)
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To write to the DSP (all writes to 2xCh MUST follow this procedure)
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1. Read 2xCh until bit 7 is clear
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2. Write to 2xCh
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To read from the DSP (all reads from 2xAh MUST follow this procedure)
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1. Read 2xEh until bit 7 is set
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2. Read from 2xAh
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Interrupts:
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In DMA DAC and DMA ADC modes, a single interrupt will occur after the
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block of data has been read/written. To clear the interrupt, read 2xEh
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once (as well as clearing the PIC).
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Ignoring Interrupts:
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The interrupt can be ignored if you poll the DMAC (DMA Controller).
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Once the DMAC reports a count of 0FFFFh the transfer is finished, read
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2xEh once and you are finished. You can also poll the DMA status register
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and wait for the Terminal Count reached bit to be set (I found that the first
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read after starting the transfer had the bit set, but not the second).
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Note to VESA/Local Bus Video users:
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These video cards use DMA channel 1 which is the DMA channel used by
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the Sound Blaster. Any video accesses will screw up the output of the
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Sound Blaster.
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Calculating the Time Constant:
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Normal Speed:
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Time Constant = 256 - (1,000,000 / sampling rate)
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= 256 - (1,000,000 / 8,000 )
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= 131
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High Speed:
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Time Constant = (MSByte of) 65536 - (256,000,000 / sampling rate)
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= (MSByte of) 65536 - (256,000,000 / 44,100)
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= (MSByte of) 59731
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= (MSByte of) 0E953h
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= 0E9h
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Direct mode DAC:
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1. Write a D1h to 2xCh
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2. Write a 10h to 2xCh
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3. Write the 8-bit data sample to 2xCh
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4. Wait for the correct timing (must do your own timing)
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Repeat steps 2-4 until end of data
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5. Write a D3h to 2xCh
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Normal speed DMA mode DAC:
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1. Write a D1h to 2xCh
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2. Setup Interrupt service routine
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3. Write a 40h to 2xCh
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4. Write Time Constant to 2xCh
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5. Program the DMAC (DMA Controller)
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6. Write 14h to 2xCh
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7. Write the LSByte of Data Length - 1
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8. Write the MSByte of Data Length - 1
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9. Service Interrupt (may need to repeat steps 5-7 in the ISR)
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10. Restore original Interrupt Service Routine
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11. Write a D3h to 2xCh
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Commands can be written to the DSP while waiting for the interrupt
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High speed DMA mode DAC:
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1. Write a D1h to 2xCh
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2. Setup Interrupt service routine
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3. Write a 40h to 2xCh
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4. Write Time Constant to 2xCh
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5. Program the DMAC (DMA Controller)
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6. Write 48h to 2xCh
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7. Write the LSByte of Data Length - 1
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8. Write the MSByte of Data Length - 1
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9. Write 91h to 2xCh
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10. Service Interrupt (may need to repeat steps 5-7 in the ISR)
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11. Restore original Interrupt Service Routine
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12. Write a D3h to 2xCh
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Commands CANNOT be written to the DSP while waiting for the interrupt
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Resetting the DSP is the procedure used to halt DMA in progress
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Direct mode ADC:
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1. Write a 20h to 2xCh
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2. Read the 8-bit data sample from 2xAh
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3. Wait for the correct timing (must do your own timing)
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Repeat steps 1-3 until finished
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Normal speed DMA mode ADC:
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1. Setup Interrupt service routine
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2. Write a 40h to 2xCh
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3. Write Time Constant to 2xCh
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4. Program the DMAC (DMA Controller)
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5. Write 24h to 2xCh
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6. Write the LSByte of Data Length - 1
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7. Write the MSByte of Data Length - 1
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8. Service Interrupt (may need to repeat steps 5-7 in the ISR)
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9. Restore original Interrupt Service Routine
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Commands can be written to the DSP while waiting for the interrupt
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High speed DMA mode ADC:
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1. Setup Interrupt service routine
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2. Write a 40h to 2xCh
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3. Write Time Constant to 2xCh
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4. Program the DMAC (DMA Controller)
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5. Write 48h to 2xCh
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6. Write the LSByte of Data Length - 1
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7. Write the MSByte of Data Length - 1
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8. Write 99h to 2xCh
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9. Service Interrupt (may need to repeat steps 5-7 in the ISR)
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10. Restore original Interrupt Service Routine
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Commands CANNOT be written to the DSP while waiting for the interrupt
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Resetting the DSP is the procedure used to halt DMA in progress
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The Mixer: --------------------------------------------------------------------
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The mixer can only be found on the Sound Blaster Pro.
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It mixes the following audio sources:
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-digitized voice
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-FM synthesized music
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-CD-audio
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-line-in
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-microphone input
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-PC speaker output
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It allows software to control volume on:
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-digitized voice
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-FM synthesized music
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-CD-audio
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-line-in
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-microphone mixing
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-overall master volume
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The mixer setting can be done with 2 I/O ports, 2x4h and 2x5h.
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x=2,4 for the Sound Blaster Pro
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2x4h is the address port (write only), 2x5h is the data port (read/write)
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The programming sequence is as follows:
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1. Write the address of the mixers register to 2x4h
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2. Read/Write the mixers register value from/to 2x5h
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Mixer registers:
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Register| D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 |
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--------+----+----+----+----+----+----+----+----+
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00h | Data Reset |
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02h | Reserved |
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04h | Voice Volume L | Voice Volume R |
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06h | Reserved |
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08h | Reserved |
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0Ah | x | x | x | x | x | MIC Mixing |
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0Ch | x | x | In Filter | ADC | x |
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0Eh | x | x |DNFI| x | x | x |VSTC| x |
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20h | Reserved |
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22h | Master Volume L | Master Volume R |
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24h | Reserved |
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26h | FM Volume L | FM Volume R |
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28h | CD Volume L | CD Volume R |
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2Ah | Reserved |
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2Ch | Reserved |
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2Eh | Line Volume L | Line Volume R |
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x=don't care
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Reserved=preserve original value
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Register Descriptions:
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Reset Register (00h):
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You can write any 8-bit value to this register to reset the mixer
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Voice Volume Register (04h):
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d[7..4] voice volume left
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d[3..0] voice volume right
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The default level is 9.
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Microphone Mixing Register (0Ah):
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The default level is 0.
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Input Setting Register (0Ch):
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ADC - input source:
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d[2] d[1]
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0 0 Microphone (default)
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0 1 CD audio
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1 0 Microphone
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1 1 Line-in
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In Filter - filter select:
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d[5] d[4] d[3]
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0 x 0 Low Filter (default)
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0 x 1 High Filter
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1 x x No Filter
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Output Setting Register (0Eh):
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This register specifies the voice output features.
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DNFI 0 output filter is ON (default)
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1 output filter is bypassed
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VSTC 0 Mono voice mode (default)
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1 stereo voice mode
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Master Volume Register (22h):
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d[7..4] master volume left
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d[3..0] master volume right
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The default level is 9.
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FM Volume Register (26h):
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d[7..4] fm volume left
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d[3..0] fm volume right
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The default level is 9.
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CD Volume Register (28h):
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d[7..4] cd volume left
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d[3..0] cd volume right
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The default level is 0
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Line-In Volume Register (2Eh):
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d[7..4] line-in volume left
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d[3..0] line-in volume right
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The default level is 0
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