System Clocks; Transmit Audio Path; Figure 4.5-4. Vocon Transmit Audio Path - Motorola XTS 2500 Service Manual

900 MHz Detailed Theories of Operation: VOCON Functional Blocks

4.5.6.3.6 System Clocks

The Patriot is supplied with two clocks:
1. The first clock, a 16.8 MHz sine wave, comes from the RF portion of the radio. It is
conditioned by the clock buffer circuit, which includes Q709, R722, R740, R743, R729, R797,
C726, C725 and C727.
2. The other clock supplied to Patriot is a 32.768 kHz square wave. This clock is generated by
the external 32.768kHz crystal Y701, and a clock buffer circuit that includes U713, R745,
R746, C743, C792, R742 and R741. This signal is supplied to the CKIL pin on the dual-core
processor.

4.5.6.4 Transmit Audio Path

Refer to Figure
20 pin side connector (J650), and the internal microphone bias is set by circuitry that includes R751,
R753, C751, C753 and C755. The internal microphone signal is connected to the INT_MIC_P pin,
which is the input terminal on the MAKO IC internal op-amp G1 after the signal is multiplexed. The
gain of the G1 pre-amp is set to +15 dB, which is programmed by dual-core processor SPI lines.
The external microphone audio enters the VOCON board through the remote connector J102, pin10,
and the external microphone bias is set by circuitry that includes R750, R752, C750, C752 and
C754. The external microphone signal is connected to the EXT_MIC_P pin, which is an input
terminal on the MAKO IC internal op-amp G1 after the signal is multiplexed. The gain of the G1 pre-
amp is set to +15 dB, which is programmed by dual-core processor SPI lines.
The dual-core processor, through the SPI bus, programs a multiplexer internal to the MAKO IC to
select one of the microphone signals. Then, the selected microphone signal goes through the G1
pre-amplifier stage and on to a programmable gain amplifier (G2) before it goes to the CODEC for
A/ D conversion. The resulting digital data is filtered and sent to the DSP on the CODEC_TX line
from the MAKO IC VC_TX3V pin. After additional filtering and processing, the DSP sends the data-
out from the STDB pin, labeled TX_SSI_DATA to the RF interface connector.
.
Internal Mic Bias
R751, R753,
C751,
C753, C755
External Mic Bias
R750, R752,
C750, C752
C754
6816985H01-F
4.5-4. The single-ended internal microphone audio enters the VOCON board through
INT_MIC_P
MUX
EXT_MIC_P
MAKO_CS
SPI_MISOB
SPI_MOSIB
SCKB

Figure 4.5-4. VOCON Transmit Audio Path

MAKO IC U701
Amp G2
Pre-amp
Gain = -30
G1 Gain
to 0 dB
= 15 dB
CODEC_TX
CODEC_FSYNC
4
CODEC_DCLK
Patriot
Patriot
SPIB
SAP / BBP
TX_SSI_FSYNC
TX_SSI_CLK
TX_DATA
CODEC
A/D 16-Bit
HPF = 200 Hz
& LPF = 3.4
kHz cutoff
RF D/A
U201
3
February 14, 2012
4.5-17