Pll Unlock; Display Section; Control Section; Control Section Block Diagram - Kenwood TK-768 Service Manual

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4-2. PLL unlock
When the PLL is unlocked, the lock detect signal
(LD) of the PLL lC 1C202\ is rectified by D212, and con-
verted to a DC signal. The CPU monitors this signal.
When the PLL is unlocked, the CPU turns the key out-
put signal off (low), then turns O10, 06, and BT off to
prevent unnecessary transmission.
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E ffi fH 'f'X.ïÁHÍ, +ËfHPli€ft Ê,flf ( PLL rC,
1C202) trïff Ëïeilil{È€ ( m ) %.D212 gitríqÈ-+Ë
iffi'íÈ€, CPU ffiïLrfl'íÈ€. EffifHqit.+XÉ, cPU Xl{
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5. Display Section
CPU (1C409) contains an LCD driver to drive the 7-
segment, B-digit LCD directly.
5. ErËl3r|
CPU (IC4O9) Aê-+ LCD gEA+$, F{I/Ë&\LaJ
7 FkSffiLCD (i&ffi,ÉzÍ+$ ) .
6. Control Section
The control section consists of CPU (1C409) and its
peripheral circuits. lt controls the TX-RX unit. The CPU
has the following main functions:
1) Switching between transmission and reception
according to the PTT signal input.
2) Reading channel, frequency, and program data
from the memory circuit.
3) Sending frequency data to the PLL.
4) Turning the squelch on and off according to the
pulse signal input from the squelch circuit.
5) Controlling the audio mute circuit according to in-
put decode data.
6) Sending encode data.
7) Sending data to the D/A converter.
Fig. 6 PLL unlock circuit
Fig. 7 Display section
6. ËftilË[r]
f, È CPU
1) tRffiffi^Êí prr rà+w&È.Êtfiï*|lf
2) )^#tfr#$+i*s {ËiÉ, ffiÈuet&ffi^w+wffi
3) ËfËfEqi (PLL Effi) iËuffi+trffi
4 ) ffi ffi ffi r* É,K Ê! bft 4 ffi ^{È€ïllï4 Jehtffi w
5 ) &ffiffi^ffiffiffiwffiwft|JÈffi#ÈËEf
6) iËfiffiEffiffi
7) ,ËSfrffiiË D/A A&+$
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CI RCUIT DESCRI PTION/ ËffiÏ, HI
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so
tc409
COM2
CPU
coMl
coM0
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q n l
tc409
CPU
DT
CK
EP
1 2 t 1 D t c 4 1 2 q n l
Fig. 8 Gontrol section block diagram
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