VS1103B datasheet(27/61 Pages) ETC2

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VLSI

Solution

VS1103b

VS1103B

6. FUNCTIONAL DESCRIPTION

Volume

control

Audio

FIFO

S.rate.conv

and DAC

SCI_VOL

512 stereo

samples

application

User

Bass

enhancer

AIADDR=0

SB_AMPLITUDE!=0

AIADDR!=0

stream

Audio

enhancer

Treble

ST_AMPLITUDE!=0

ST_AMPLITUDE=0

ST_EARSPEAKER=0

ST_EARSPEAKER!=0

Earspeaker

SB_AMPLITUE=0

Figure 13: Normal Data Flow of VS1103b, Part 2.

Figure 13 presents the data ﬂow of the Audio stream generated in Figure 12.

If SCI AIADDR is non-zero, application code is executed from the address pointed to by that register.

For more details, see Application Notes for VS10XX.

Then data may be sent to the Bass and Treble Enhancer depending on the SCI BASS register, followed

by Earspeaker Spatial Processing, depending on ST EARSPEAKER.

After that the signal is fed to the volume control unit, which also copies the data to the Audio FIFO.

The Audio FIFO holds the data, which is read by the Audio interrupt (Chapter 8.13.1) and fed to the

sample rate converter and DACs. The size of the audio FIFO is 1024 stereo (2×16-bit) samples, or

4 KiB.

The sample rate converter converts all different sample rates to XTALI/2, or 128 times the highest us-

able sample rate. This removes the need for complex PLL-based clocking schemes and allows almost

unlimited sample rate accuracy with one ﬁxed input clock frequency. With a 12.288 MHz clock, the DA

converter operates at 128 × 48 kHz, i.e. 6.144 MHz, and creates a stereo in-phase analog signal. The

oversampled output is low-pass ﬁltered by an on-chip analog ﬁlter. This signal is then forwarded to the

earphone ampliﬁer.

6.3.2 Real-Time RT-Midi Mode

If GPIO1 is 1 and GPIO0 is 0 at startup, RT-Midi Mode is activated. In this mode RT-Midi data is read

through the UART at the default MIDI speed 31250 bit/s. The generated audio is sent to the audio path

as shown in Figure 13.

When RT-MIDI mode is activated, GPIO2 and GPIO3 are read and their contents are copied to register

bits SCIMB EARSPEAKER0 and SCIMB EARSPEAKER1, respectively. This way it is possible to

activate EarSpeaker in this mode without writing to any SCI registers. Also, if SCI CLOCKF has not

been set to a non-zero value, the clock multiplier is automatically set to 3.5X.

This mode is intended for connecting a MIDI keyboard or sequencer to VS1103b.

Version 1.01, 2007-09-03

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