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TK-8108
■ Encode
The QT and DQT signals are output from QT/DQT of the
CPU (IC6) and summed with the external pin DI line by the
summing amplifier (IC4) and the resulting signal goes to the
D/A converter (IC3). The DTMF and signal is output from
DTMF of the CPU and goes to the DIA converter (IC3). The
signal is summed with a MIC signal by the summing ampli-
fier (IC4), and the resulting signal goes to the D/A converter
(IC3).
The D/A converter (IC3) adjusts the MO level and the bal-
ance between the MO and QT/DQT levels. Part of a QT/
DQT signal is summed with MO and the resulting signal
goes to the VCOMOD pin of the VCO. This signal is applied
to a varicap diode in the VCO for direct FM modulation.
■ Decode
• QT/DQT/DTMF
The signal (DEO) passes through two low-pass filters of
IC11, goes to QTIN of the CPU (IC6) to decode QT, DQT.
The DTMF signal is decoded by a dedicated IC (IC9) and the
resulting signal is sent to the CPU (IC6) as serial data.
■ D/A Converter
The D/A converter (IC3) is used to adjust MO modulation,
AF volume, TV voltage, FC reference voltage, and PC
POWER CONTROL voltage level.
Adjustment values are sent from the CPU as serial data.
The D/A converter has a resolution of 256 and the following
relationship is valid:
D/A output = (Vin – VDAref) / 256 x n + VDAref
Vin: Analog input
VDAref: D/A reference voltage
n: Serial data value from the microprocessor (CPU)
22
CIRCUIT DESCRIPTION / 电路说明
QT/DQT
IC6
CPU
IC4
DTMF
IC3
SUM
D/A
AMP
Fig. 14 Encode / 图14 编码
IC11(2/2)
QTIN
IC6
SD
CPU
STD
ACK
Fig. 15 Decode / 图15 解码
■ 编码
从CPU (IC6) 的QT/DQT输出的QT和DQT信号通过总和放大
器 (IC4) 与外置管脚DI线计算总和。获得的信号进入数/模转换
器 (IC3)。从CPU的DTMF输出的DTMF和信号进入数/模转换器
(IC3)。总和扩大器 (IC4) 计算信号和MIC信号的总和，获得的
信号进入数/模转换器 (IC3)。
数/模转换器 (IC3) 调整MO电平和MO与QT/DQT电平之间的
平衡。计算QT/DQT信号的端口和MO的总和，获得的信号进入
压控振荡器的VCOMOD管脚。此信号提供给压控振荡器中的各
色二极管直接进行调频调制。
TCXO
IC4
MOD
X1
SUM
TCXO
AMP
DI
IC3
D/A
■ 解码
• QT/DQT/DTMF
信号 (DEO) 经过IC11的两个低通滤波器，进入CPU (IC6) 的
QTIN，对QT、DQT进行解码，获得的信号作为串行数据被发
送到CPU (IC6)。
IC11(1/2)
LPF
LPF
DEO
IC9
DTMF
DECO.
■ 数/模转换器
数/模转换器 (IC3) 用于调整MO调制、AF音量、TV电压、
FC参考电压和PC POWER CONTROL 电压电平。
从CPU以串行数据发送调整数值。数／模转换器的分辨率为
256并且下述关系是有效的。
数／模输出 = (Vin –VDAref) / 256 x n + VDAref
Vin：模拟输入
VDAref：数／模参考电压
n：来自于微处理器 (CPU) 的串行数据值
IC1
PLL
VCO
VCO
MOD
HT
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