HYT TC-610P Service Manual page 18

2） Block diagram of Rx audio & signaling processing circuit
CF302
450KHz+/4.5K
OUT
To MCU
RSSI IFAMP2
DET
SQ
PE
De
Emphasis
After demodulating the received signal, U200 outputs initial audio signal, which contains noise, signaling
and voice components. Therefore, audio is processed via three flows.
1） Rx audio processing: One flow of audio signal from U200 goes back to U200 after passing through
the RC low-pass filter and de-emphasis circuit. This flow of audio signal is amplified at U200, and
restored after frequencies below 300Hz are removed. The restored audio signal is adjusted by the
potentialmeter and then fed to the audio power amplifier (U201), which performs power amplification
to drive the speaker directly. To obtain higher power, BTL output is adopted.
2） Rx signaling processing: One flow of audio signal from U200 goes to the 300Hz low-pass filter circuit
(U640). After audio signals above 300Hz are removed, signaling (CTCSS or CDCSS) goes to the
QTIN pin of CPU. Then the input singaling is decoded by CPU.
3） Noise Signal Processing: One flow of audio signal from U200 goes back to U200. After they are
filtered, amplified and rectified at U200, a DC voltage signal (SQ) is derived and is sent to the BUSY
pin of MCU by the ND pin of U200. Then MCU processes the input signal.
6. MCU Control Circuit
The block diagram of the MCU control circuit is shown in the figure below. MCU operates on the clock
frequency of 7.3728MHz.
IN
IFAmp1
U200
AN29160AA
mix2
PROCESSER
VREF
Mic amp
tone-LPF
mic mute
5th-LPF
signalling output
To MCU
CDC/CTC
SPVCC
VCC
EN DATA
VCO TX RX MCU
LATCH
POWERREG
IC
volume
AF
mute
LIM
5th-HPF
(TX)
AF
HPF
SF
AMP(TX)
AGC
AUDIO OUT
Figure 7
16
TC-610P Service Manual
1
CLK
sp Amp
SW
U201
AF
AMP
0
16Ω IW