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Reset Circuit
U310 and U314 form the reset circuit. U314 is a voltage level detector whose output goes low if the supply drops
below 4.5V. When nHF ON is low (P201 pin 7), Q307 is switched on, pulling the input to U310 high. This signal
also feeds the two analogue switches turning them on. On this line going high U310 Q output will go high for a
predefined time of approximately 5
µ
S, turning Q308 ON and pulling the reset line low.
10.1.3 Path Description
The following lists the direct connection between parts of a given portion of the circuit.
TX Audio
Path from P301 Pin 1 Microphone connection on PCB-GND REF POINT TP309
P301
2 PIN Connector
Pin 1 or TP310
U311
Amplifier
Input pin 1
Output pin 4
U305
CODEC
Input pin 24
Output pin 13
U306
DSP
Input pin 9
Output pin 13
U304
CODEC
Input pin 12
Output pin 5
U301
Amplifier
Input pin 5
Output pin 7
U312
Analogue Switch
Input pin 2
Output pin 1
U315
Amplifier
Input pin 3
Output pin 4
P201
16 PIN Connector
Pin 3 (TX_Audio) or TP201
RX Audio
Path from P201 Pin 4 (RX_Audio) Main unit connector on PCB-GND REF POINT TP312
P201
16 PIN Connector
Pin 4 (RX_Audio) or TP304
U301
Amplifier
Input pin 2
Output pin 1
R324
Volume Control
Input pin 1
Output pin 2
U304
CODEC
Input pin 24
Output pin 13
U306
DSP
Input pin 10
Output pin 14
U305
CODEC
Input pin 12
Output pin 5
U313
Analogue Switch
Input pin 1
Output pin 2
U308
Output Amplifier
Input pin 1
Output pin 4
J300
Ext Speaker Socket
Input pin 2 or TP311
Output pin 3
P300
2 PIN Connector
Pin 2
Issue 1
Section 10
MCUK980101G8
Revision 0
10 - 2
Technical Guide
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