Guardian G25AMK005, Техническое руководство

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G U A R D I A N V H F 1 1 0 W M O B I L E 2-17
2.7 Display Board
The Display board consists of a seven-switch keypad and an LCD module with integrated LED blue backlight. The
board is heatstaked onto the plastic front panel, forming a permanent assembly. Electrical connections are made to
the Interface board via a 20-pin connector (J13).
The radio display module is a full graphics 80x32 pixels LCD, requiring a temperature compensated differential
driving voltage of about 12V and a 1/6 bias, 1/32 duty cycle driving scheme. The LCD driver device (Seiko Epson
SED 1530) drives the display. This LCD driver has an internal display RAM that copes with all the display
refreshing autonomously. Display data transfers from the main controller are only required when the display is
changed, selective display RAM updates are also available to minimize serial traffic. The LCD driver display RAM
is accessed through a one way synchronous serial interface and connected in parallel with the AVR serial port. The
LCD CS input is used to differentiate between serial data for the LCD driver and the keypad board hardware reset
line resets the display drive. The hardware is configured such that during hardware reset, before serial LCD data is
presented, the LCD is blank. The radio keypad consists of 16 keys, which contact onto switch contacts on the rear of
the keypad board.
Keypad
Figure 2-5: Keypad Board