STw5094

6/37

FUNCTIONAL DESCRIPTION

I DEVICE MODES

STw5094 can work in 4 different modes, selected by bits MD in Control Register 18 (CR18). Depending on the

mode different data interfaces, clock inputs, and internal blocks are selected. A built-in power consumption

management function keeps in power down the blocks that are not needed by the selected operating mode. In

all the modes the Output Drivers can be activated in all the combinations allowed by bits OS in CR6 (in case of

stereo input and LSP

⁄ N driver selected the Left channel is sent to this driver, while in case of voice input and

HPL + HPR drivers selected the same signal is sent to both drivers).

I.1 Audio Mode:

⁄ F to the output drivers is active to allow the Stereo Audio DAC function.

⁄ F is active while the PCM I ⁄ F is inactive.

The master clock of the device is OCK. The OCK frequency must be 256 times the sampling frequency for the

MPEG1 and MPEG2 sampling frequencies and 512 times for the MPEG2.5 sampling frequencies.

The sampling frequency (LRCK frequency) can be selected with bits LAY and AFS in REG6.

Since the OCK clock is used directly in all the Audio blocks, its jitter and spectral properties must be adequate

to the desired Audio quality.

The Tone

⁄ Ring ⁄ DTMF generator can be activated if needed. The FM preamplifiers are in power down.

I.2 Voice Mode:

In Voice mode the TX path from microphone or line input to DX and the RX path from DR to the output drivers

are active to allow the PCM CODEC function. The PCM I

The master clock of the device is MCLK, the frequency of the clock can be selected with bits F in CR0.

The FM preamplifiers are in power down.

I.3 Tone Only Mode:

In Tone Only mode the path from the Tone generator to the output Drivers and to the Buzzer is active to allow

⁄ F and PCM I ⁄ F are inactive, as all the Audio and Voice converters

functions.

The master clock of the device can be selected to be AUXCLK, MCLK or OCK (bits CFM in CR18).

The Tone

⁄ Ring ⁄ DTMF generator can be activated if needed. The FM preamplifiers are in power down.

I.4 FM Mode:

In FM mode the path from FML and FMR analog inputs to the output Drivers is active to allow FM Stereo Radio

⁄ F and PCM I ⁄ F are inactive, as all the Audio and Voice converters functions.

The master clock of the device can be selected to be AUXCLK, MCLK or OCK (bits CFM in CR18).

The Tone

⁄ Ring ⁄ DTMF generator is in power down.

II DEVICE OPERATION

II.1 Power on initialization and Software Reset:

When power is first applied, power on reset circuitry initializes STw5094 and puts it into the power down state.

All the Registers are initialized as indicated in the Control Register description section. All the functions are

disabled.

The registers can be initialized also writing bit SRS (software reset) in CR18.