Receive Audio Path; Figure 4.1-5. Vocon Receive Audio Path - Motorola XTS 2500 Service Manual

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4.1.6.5 Receive Audio Path

dual-core processor SRDB pin. The DSP decodes the data and sends it out through the CODEC_RX

line to the MAKO IC VC_RX3V pin. The CODEC filters, adds digital programmable gain G1, then

converts the digital data into an analog audio signal, which in turn is sent to programmable

attenuator G3. The signal is then sent through an internal programmable differential preamplifier

(G4) to add gain and outputs the signal on pins VC_OUT_P and VC_OUT_M of the MAKO IC.

This output from the preamp is then filtered through circuitry R798, R844, C764, C765, C790, and

then sent back to 2 independent internal BTL differential power amplifiers, G5 & G6, of the MAKO IC.

The power amplifiers are programmed to a fixed gain of 26 dB through the dual-core processor SPI

lines and PA control registers.

The dual-core processor selects whether the amplified audio is routed to the internal speaker or the

external speaker through the SPI lines based upon which amplifier is turned on as shown in the PA

control block. The output audio is routed on MAKO IC pins INT_SPKR_P and INT_SPKR_M for

internal and EXT_SPKR_P and EXT_SPKR_M for external speaker lines.

RX_SSI_FSYNC

Patriot SAP/BBP

Patriot SPIB

February 14, 2012

4.1-5. The receive audio data comes from the Abacus III IC U401 (DOUTA) to the

Filter = 22kHz,

VHF Detailed Theories of Operation: VOCON Functional Blocks

LPF = 3.4kHz

MAKO IC U701

6816985H01-F

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