4 - 4
4-4 FFSK CIRCUIT DESCRIPTION
4-4-1 GENERAL
IC9 is the compounder IC which is controlled by serial data
bus line (“TRD”, “MSKE”, “DIN”, “SCK”, “APST”, “REGS1”,
“REGS2”, “RTM”, “RDT”, “FCLR” signals) from the CPU.
The IC is composed of FFSK transmitting and receiving cir-
cuits, data register circuits, transmitting and receiving data
buffer circuits, and so on.
X4 is oscillated 3.58 MHz reference signal to the IC9.
4-4-2 DECODEING CIRCUIT
The input signal from the FM IC (IC3, pin 9) via the “DSIN”
signal is applied to the compounder IC (IC9, pin 5), and is
then detected bit synchronization detection within 16 bit.
4-4-3 ENCODEING CIRCUIT
The FFSK signal is made by serial data bus line signals, and
is then output from the compounder IC (IC9, pin 6).
In case of the FFSK signal is used for the PM modulation,
the FM/PM switch (IC29) is changed to pin 3.
In case of the FFSK signal is used for the FM modulation,
the FM/PM switch (IC29) is changed to pin 5.
The output signal from IC29, pin 4 is applied to the the buffer
amplifier (IC7, pins 8, 10), and is applied to the D/A conver-
tor IC (IC13, pins 21, 22). The signal is applied to the mod-
ulation circuit (Q12, D7, D8, D43–D45).
COMPRE-
MSK
MOD
MSK
DEMOD
B
EXPAN-
DER
COMPANDER
IC9 TC35453F
SSOR
MCIN
X4
Q47
2SC4081
MCOT
CR-563
3.58 MHz
29, MSKE
30, TRD
23, DIN
25, REGS1
26, REGS2
31, RTM
32, RDT
33, FCLR
IDCIN
TXFO
8
1
RXFO
MICIN
TXOUT
12
3
RXIN
5
MSKIN
28
27
6
9
22, SCK
22, APST
SERIAL DATA LINE
LPF
AMP
LIMIT
AMP
AMP
HPF
LPF
AMP
BUFF
HPF
LPF
AMP
BPF
HPF
AMP
• Conpounder IC block diagram
