Cpu Unit; Panel Unit; Rotary Encoder; Input Ports/Output Ports - Kenwood pds20-18 Service Manual

CPU UNIT (X77-2110)
CPU
IC7 (CPU) runs on 16 MHz clock pulses
generated by the X1 quartz oscillator.
Panel Switches (S1 to S10) and
Interruption Circuits (IC21 and I C 2 2 )
When any of the switches S1 to S10 on the panel is
pressed, either input of the input port IC9 goes
"High". At that time, IC21 and IC22 cause an
interruption to the CPU.
Rotary Encoder ( S 11 )
Signals to the rotary encoder are processed
by IC12, IC23 to IC25 and IC28 first.
Processed and output data is latched by
IC11 and input to the input port
(pins 17 and 15) of IC14.
A signal for clearing IC11 is output by the CPU in the
program loop.
Input Ports (IC9 and IC14)
Three types of data and signals shown
below are input to the input ports, in addition
to signals from the panel switches and
encoder :
1) Serial data from the control unit
2) Signal issued when the OUTPUT switch is
turned on
3) S ignal issued when the OUTPUT switch is
set to the remote control position
These signals are read in the program loops and
sent to the CPU by IC9 and IC14.
Output Ports (IC10 to IC19)
IC16
The below-shown signals to the control unit are
output from the IC16 output port. These signals
are isolated by the control unit.
1) serial data to be sent to the D/A converter circuit
Clock pulses for operating various elements in
2)
the D/A converter circuit.
PDS20-18/PDS36-10/PDS60-6
CIRCUIT DESCRIPTION
3)
IC17
Signals for the panel unit display driver
(IC1and IC2) are output by IC17.
IC18 and IC19
Signals for turning on the LEDs (D1 to D10) on the
panel unit are output by IC18 and IC19 (pins 18
and 19). Signals for controlling the flow of the RS-
232C interface are output by IC19 (pin 12).
IC10
Signals for controlling various optional boards are
output by IC10.
Others
Reset signal
IC27 outputs a signal for resetting the CPU
when the POWER switch is turned on.
Driver
IC8 divides 8 MHz clock pulses output by the
CPU into 4 MHz pulses, which are output
from the IC10 port and used for optional
boards.
Panel unit X66-1600-00
IC1 and IC2 from a driver for the seven segment
LED indicator (ED1 to ED8). ED1 to ED8 are
controlled by signals output by IC17 (CPU
unit).
Strobe signals for controlling the D/A converter
circuit
8