Service manual
CA-5
Microprocessor Control
Introduction
The CA chassis employs IC6000 as its microcontroller. All end user and servicer controls are accessed
using this IC. While most of its functions will be described in terms of how they are used by other devices in
the receiver, a number of facts concerning the microprocessor and its input devices will now be presented.
The microprocessors job is to communicate control instructions and feedback information to and from
various other processors and input devices in the set. These include the video, audio, PiP, audio & video
switch ICs, the tuner, the EEPROM, the keyboard and IR detector, and the reset IC. Some of these use a
direct connection via either switch, variable pulse, or DC level for communication. Others rely on the I
2
C
bus, also known as serial clock and data bus. IC6000 provides 2 sets of clock and data lines. The first set
is pins 37 and 39, and the second is on pins 36 and 38. The EEPROM and the factory setup connector,
4G9, are the only devices which receive clock and data pulses from the first set.
Input Devices
The IR detector demodulates pulses from the 40 kHz modulated carrier and sends the pulses to pin 15 of
the microprocessor. There a special algorithm interprets the pulses as the various commands they represent.
The keyboard is only slightly more complicated in its operation external to IC6000. It works by varying
voltage on only two input pins (7 and 8) using resistor networks. A/D converters inside the micro interpret
the different voltages. Because voltage detection is used rather than active keyboard scanning, keyboard
radiation is not a problem, but maintaining a +5VSB to within ±4% is critical.
R6018
R6017M
R6020M
R6019M
R6022M
R6025M
R6021M
R6023M
R6024M
+5VSBF
R6015
R6016
R6069M
R6070M
C6042MC6043M
Pin 7
Pin 8
1
2
3
4
5
+5VSBF
L6005
C6036M
R6029M
C6035
PROV
L6004
Pin 15
C6004
R6028
C6092M
C6003M
R6027
2K6
3
2
1
IR6000
GND
VS
VOUT
EXTERNAL
KEYBOARD
Keyboard
& IR Input to
IC6000
SW1
ON/OFF
SW2
CH-UP
SW3
CH-DN
SW4
VOL-UP
SW5
VOL-DN
SW6
MENU
<<Figure CA-6>>