Service manual

June 21,2004 2-5
NP88 FLEX DECODER
Circuit Description
The
µC
controls all major functions of the decoder, including processing of receiver
datapassingthroughtheSupportModuleanduserinterfacefunctionsviathealert
circuits and LCD. The µC module consists of:
• Read-Only-Memory (ROM) to store the executable program code.
• Random Access Memory (RAM) to store all user messages and other key pro-
cessing data.
• A display driver to control the LCD.
• Ports to enable serial communications with on-board ci rcuitry and external
devices (for example, the programming interface).
LCD
Data messages are v iewed on a high contrast, liquid crystal d isplay (LCD) module
affixed to t he decoder board via a highly reliable heat seat connector (HSC). The
LCD is controlled via 28 lines from the LCD driver in the
µC
.
Alert Circuitry
The alert circuitry consists of a Transducer, a Vibrator, and inca ndescent LED.
These circuits provide the audio and visual feedback to the user.
The Transducer and Transducer Drive Circuit provide the audio alerts and are
driven by the Support Module.
The Vibratorismounted in the back housing and is connected tothe Vibrator Drive
Circuit via two spring contacts. The Vibrator provides alerts when in the silent
mode of operation. The Vibrator is controlled by the
µC
.
The Alert LED and LED Drive Circuit provide a visual alert out of phase with
the Transducer alert. The Alert LED is controlled by the
µC
. The Alert LED also
serves as the display backlight when viewing the display under dark lighting
conditions.