Microprocessor (Figure 23)
The Microprocessor, 7064, is located on the
SSB. User control of the Microprocessor is
accomplished via the Keyboard or Remote. In
case of Overcurrent or a failure in the
Horizontal sweep circuit, The PROT-UP line
will go High turning transistor 7276 On,
placing a Low on Pin 5 of the Keyboard line.
The Microprocessor will then shut the set Off.
Composite Video for Data Capture, for Closed
Caption or Text, is fed to the IC on Pins 32
and 31. The Microprocessor is connected to
the Memory IC 7066 which stores information
for Option Codes, Geometry, Gray Scale, and
Customer settings. Two I2C busses, SDA and
SDA-2, communicate with the set along with
several analog outputs. The set is turned On
when the STAND BY line on Pin 13 is pulled
Low by 7064. Horizontal and Vertical sync for
the On-Screen display is fed to the IC on Pins
53 and 55. The Reset for the Microprocessor
is located on the SSB. Transistor 7063 turns
Off as 2043 charges causing Pin 73 to go
High when power is first applied to the set for
Reset. When the set is operating normally,
the Reset pin should measure Low. The
FRONT-DETECT line monitors the Side
Jack panel for the Headphone or an SVHS
connection. It also monitors 7992 for a
Power Down. A Low on Pin 6 will disable
the Keyboard and IR inputs.
Customer Control Interface (Figure 24)
The Keyboard line is a voltage level
controlled input. With no buttons pressed,
this line should read approximately 3.38
volts when the set is On. It will be
approximately 0.2 volts higher when the
set is in Standby. In the XXPT31 versions,
the Keyboard Switches are located on the
LSB. In the XXPT41 and above models,
the Keyboard Switches are located on the
Top Control panel for Volume Down,
Volume Up, Channel Up, and Channel
Down. The Power Switch is located on the
Front Interface panel.
Page 29
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