27
TK-980/981
■
Memory Circuit
The transceiver has a 2M-bit (256k x 8) flash ROM
(IC510) and an 8k-bit EEPROM (IC512). The flash ROM con-
tains firmware programs, data and user data which is pro-
grammed with the FPU. The EEPROM contains adjustment
data. The CPU (IC511) controls the flash ROM through an
external address bus and an external data bus. The CPU
controls the EEPROM through two serial data lines.
■
Key Matrix Circuit
The TK-980/981 front panel has ten keys. Each of them is
connected to a cross point of a matrix of the KEY1 to KEY7
ports of the microprocessor. The KEY5 to KEY7 ports are
always high, while the KEY1 to KEY4 ports are always low.
The microprocessor monitors the status of the KEY1 to
KEY7 ports. If the state of one of the ports changes, the
microprocessor assumes that the key at the matrix point
corresponding to that port has been pressed. Unused
points (KEY1 to KEY7) are also used for foot switch (FSW)
input.
IC5
D/A
converter
IC300
PLL
IC7
Shift
register
IC8
Shift
register
IC508
Shift
register
DT
RFCK
ES
EN
OE
CS
CK
DT
ACK
SD
CP
EP
AFCLR
AFMSKE
AFDAT
AFRDT
AFTRD
AFRTM
AFSTB
IC504
Audio
processor
IC507
DTMF
DECO.
IC511
CPU
TX-RX UNIT (A/2)
LCD ASSY
Fig. 8
Control circuit
SCL
SDA
IC511
CPU
ADDRESS BUS
DATA BUS
IC510
FLASH
ROM
IC512
EEPROM
Fig. 9
Memory circuit
CIRCUIT DESCRIPTION
■
Display Circuit
The CPU (IC511) controls the shift register (IC508) and
display LEDs. When the LG line goes high when the trans-
ceiver is busy, Q508 turns on and the green LED on D511
lights. In transmit mode, the LR line goes high, Q509 turns
on and the red light lights. Backlighting LEDs for the key
operation unit (D512~D517) and LCD are provided.
When the KBLC line goes high, Q512 turns on, then
Q515 and Q513 turns on, and the key illumination LED
lights. A voltage is applied to the LEDA line to turn on the
LCD backlight.
Control Circuit
The CPU carries out the following tasks:
1) Controls the shift register (IC7, IC8, IC508) AF MUTE, T/R
KEY outputs.
2) Adjusts the AF signal level of the audio processor (IC504)
and turns the filter select compounder on or off.
3) Controls the DTMF decoder (IC507).
4) Controls the LCD assembly display data.
5) Controls the PLL (IC300).
6) Controls the D/A converter (IC5) and adjusts the volume,
modulation and transmission power.
■
Encode
The QT, DQT, and LTR signals are output from LSDO of
the CPU (IC511) and go to the D/A converter (IC5) of the TX-
RX unit (A/2). The DTMF signal is output from HSDO of the
CPU and goes to the audio processor (IC504). An MSK sig-
nal is output from the audio processor according to the data
(AFDAT) from the CPU. The signal is summed with a MIC/
MSK signal by the audio processor (IC504), and the resulting
signal passes through an analog switch (IC506) and goes to
the TX-RX unit (A/2) (MO).
MO is summed with the external pin DI line by the sum-
ming amplifier (IC3) and the resulting signal goes to the D/A
converter (IC5). The D/A converter (IC5) adjusts the MO
level and the balance between the MO and TO levels. Part
of a TO signal is summed with an output signal from pin 3
(MO) of IC5 and the resulting signal goes to the MD pin of
the VCO. This signal is applied to a varicap diode in the VCO
for direct FM modulation.
Q512
SW
Q515
SW
Q508
SW
Q509
SW
Q513
AVR
KBLC
LG
LR
IC508
Shift
register
D511
GRN
RED
D512~517
LEDA
Fig. 10
Display circuit
IC511
CPU
KEY7
KEY6
KEY5
KEY4
KEY3
KEY2
KEY1
MONI
A
D
SCAN
SYS
DOWN
SYS
UP
B
C
VOL
UP
VOL
DOWN
FSW
Q511
Fig. 11
Key matrix circuit
X1
VCXO
IC5
D/A
A1
VCO
IC3
SUM
AMP
IC506
Analog
SW
IC504
Audio
processor
IC300
PLL
MB
MD
MO
TO
HT
DI
MIC
TX-RX UNIT(A/2)
AFDAT
LSDO
HSDO
IC511
CPU
Fig. 12
Encode
