Kenwood TS-440S Serivce Manual page 18

TS-440S
CIRCUIT DESCRIPTION
pulses and U/D signals from two clock signals which are 90 °
out of phase with each other, and sends the pulses and sig-
nals to the 7800 . A clock pulse interrupts the 7800 and a
U/D signal causes the 7800 to perform a count up or dow n
operation for each step . If fast rotation occurs, the 780 0
processes several steps of PLL data at one time .
Voltages from the RIT and IF shift VRs are converted fro m
analog to digital by the A/D convertor IC (4052) and fed int o
the 7800 . The voltages are used to drive the display and ar e
reflected in the PLL data .
The digital control circuit contains two 8255's for extende d
I/O . The 8255 in control unit A is an outputonly element an d
the 8255 in control unit B is an inputonly element for ke y
scan and static data . The output 8255 emits VS-1 signals,
PLL data for the 6147, clock signals, and 1 MHz LED data .
The input 8255 receives key scan data such as panel switc h
data and DIP switch data for CAR compensation . It als o
receives static data which cannot be entered as a portion ke y
scan data .
The 7800 outputs four bits of band and mode informatio n
(11 bands in the frequency range from 30 kHz to 30 MHz) .
Each time the 8251, used as the interface to a personal com -
puter, receives one byte of data, the 7800 is interrupted an d
reads the data from the 8251 . The 7800 analyzes any com-
mand in the data . In response to the command, the 7800
controls setting or writes data to the 8251 as required . Th e
8251 serially sends one byte of data including a start bit, syn -
chronizing to a 4800 Hz clock signal .
RIT IF-SNIF T
En<mer
count pufse
Enc .. u/C s .9no l
n ock s,gno l
A/O converter data
Made lnfnrmaYYO, :A LEO)
e
/0 control
,E,
_SB,US0,CW,AM,FM,FSH1
)CIOAk,por',select t
Tx e'•al 0,1 Seeial o t
,O )
Outdo. ;clock dot)-,
Band ,nformofion (PLC .195)58,FIP . 630 0
Enable 2; Power down IPO I
(PLL :145158,Fi P .6300 1
Peounwa l
1825`IAI,l8)e825) )
PIP
C
L
_ J
Rs-232C
85-I converter C S
(Address s rt) Ton e
AF Mole (MY)
conirallTON )
LE D
PP
Mule 1590) (M SCR, IMU ,
PLL do
Lock )
.. .too, dotal
OPTION
Vs -
Ines,
I
Lack S W
AT S W
MIC UP/DOWN S W
PTT SW
vs-I
dos, .
Key sca n
0 key
V, SCAN, CLEA R
. .,N. ENT tT ,
Et,
T,T-FSE T
A/
B SPRIT, A= 9
VOICE U
DOWN
\CAN SW i
pra NOn
/ '
Fig . 13 Control circuit block diagra m
18