5.9.4 Speaker Signals (EARP, EARN)

EARP and EARN are the speaker output signals. These are differential-mode outputs. With a full-scale PCM input to the CODEC, 0 dB audio output gain setting, and a differential load RL = 30Ω, the output voltage between EARP and EARN is 1.5 V rms. For load resistances less than 30Ω, the full-scale output needs is limited using the modules internal programmable gain attenuator.

The electrical characteristics are given in the table below.

Parameter

 

Conditions

 

Min

 

Typ

 

Max

 

Unit

 

 

 

 

 

 

 

 

 

 

 

 

 

RL = 30Ω

 

1.34

 

1.5

 

1.68

 

Vrms

Input voltage full scale

 

RL = 16 Ω

 

1.41

 

 

 

 

 

Vrms

 

 

RL = 8Ω

 

1.24

 

 

 

 

 

Vrms

Frequency response

 

-3dB cut-off

300

 

 

3400

 

Hz

5.10 PCM Digital Audio (SSP)

Pin

 

Name

 

Direction

 

Function

66

 

PCMCLK

 

In/Out

 

Serial PCM clock

67

 

PCMFS

 

In/Out

 

Serial PCM frame synchronization

68

 

PCMDTM

 

Input

 

Serial PCM data to module from host

69

 

PCMDFM

 

Output

 

Serial PCM data from module to host

The SSP (Synchronous Serial Port) digital interface is configured to provide a PCM (digital) audio interface. This interface can be used to process PCM digital audio signals as an alternative to routing signals to the CODECs through the analogue uplink and downlink chains.

5.10.1 PCM Data Format

The PCM digital audio interface for GS64 is based upon the Texas Instruments SSI standard. The SSP is a versatile interface which can be programmed for different clock rates and data frame sizes between 4 to 16 bits.

PCMCLK (bit clock) and PCMSYNC (frame synchronization) are both generated by the DSP within the wireless modem. The DSP within the wireless modem in this instance is the master for all external PCM, so clocks and data from external devices must be synchronized to it.

LZT 123 1836

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