Guardian G25AMK005, Technical Manual

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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 3-11
3.3.3 DSP Software
The program data for the DSP is stored in 64K Flash program blocks. The data is stored as unpacked bytes. The
blocks used for the DSP software are dedicated so that selective upgrades of this code only are possible.
3.4 Keypad MPU Software
3.4.1 Overview
The keypad microprocessor unit (MPU) provides an indirect interface via the Motherboard to the DTMF keypad and
front panel switches. It communicates with the main controller via a synchronous bi-directional serial link.
3.4.2 General
The software is designed so that processor activity and current consumption is minimized. The only continuous
operation required is keypad scanning and switch reading. An external clock at 1.5 MHz clocks the keypad. The
hardware reset is supplied from the main controller.
3.4.3 Keypad Scanning
The keypad scanning software continuously scans the keypad at a rate of a row every 10 ms. A debounce period of
40 ms is used on key presses and key releases. The software deals with simultaneous key presses and key rollovers,
making only single key presses valid. Debounced and validated key presses are passed to the serial data output
buffer.
3.4.4 Push-to-Talk (PTT) Input
Inputs from the momentary input switches, and the PTT and auxiliary keys, are read every 10 ms and are debounced
for 40 ms. The validation software filters out simultaneous presses of the auxiliary keys and the key rollover
between them. Simultaneous presses of the PTT switch and one auxiliary key are allowed. Debounced and
validated auxiliary key presses and PTT press and releases are passed to the serial data output buffer.
3.4.5 Switch Input
Inputs from the rotary switches and toggle switch are read at least every 40 ms. Changes in state are debounced for
100 ms. Debounced new switch positions are passed to the serial output buffer.
3.4.6 LED Output
The outputs to the LED are controlled under instruction from the serial port. It is possible to set both outputs off, set
the red LED on, set the green LED on, set both LEDs on (orange), and to flash either or both on a 50% duty cycle at
a controlled rate of approximately 1 Hz.
3.4.7 Backlight Control
The two LCD backlight controls for setting bright and dim operations are controlled under instruction from the serial
port. The keypad uses a fixed level backlight operation. A timeout facility switches off the backlight after
30 seconds if not requested by the main controller.
3.4.8 Serial Interface
The keypad controller implements a synchronous bi-directional serial interface using its serial port allowing it to
interface to the main controller. The main controller always sources the serial data clock. To allow autonomous
transfers from the keypad controller, a separate keypad interrupt line is provided with the interface. The interrupt
line is used to request 8 clocks from the main controller to transfer data from the keypad. The LCD chip select (CS)
input line is used to distinguish between serial data for the keypad controller and LCD driver. The serial interface
supports the following transfers:
•
Keypad to controller including: