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2-2
2.3
Control-Head Assembly
This section discusses the basic operation and components of the control-head assembly.
2.3.1
Controller
The controller consists of three main components, namely the OMAP Applications Processor, Flash
and SDRAM. The Applications Processor is the main controller of the control head. Its main function
is to receive inputs from the user and relays the command to the transceiver microprocessor for
processing via Serial Synchronous Interface (SSI) link. The Applications Processor will relay back
any information from the transceiver microprocessor to the user through the Liquid Crystal Display
(LCD). The control head is equipped with an 8MB SDRAM and a 2MB Flash memory for storing and
executing commands.
2.3.2
Power Management (Power Control Microcontroller and Voltage Regulators)
2.3.2.1 Power Control Microcontroller
ATTiny 13 microcontroller is employed to control the power state of the radio. The power state of the
radio will always follow the VOLUME/ON/OFF knob selection. Using the Customer Programming
Software (CPS), the radio can be set to optionally disable or enable the radio via sensing the ignition,
provided the ON/OFF knob is at the ON position. Moreover, the CPS can also allow emergency
footswitch to power up the radio into emergency mode without the VOLUME/ON/OFF having turned
to ON position.
2.3.2.2 Voltage Regulators
The control head utilizes seven different voltage levels to operate correctly, namely 13.8V, 5V, 3.3V,
3.0V, 2.8V, 1.88V and 1.55V. There are a total of three main regulator ICs to provide the needed
voltages.
13.8V on the main A+ line is fed through to a low power linear regulator to obtain 3.0V. This regulator
will remain powered at all times to power the ATTiny 13 microcontroller and other logic ICs of the
power control circuitry.
When the radio is in the ON state, the A+ is stepped down to 5V through a switching regulator, being
the main power source supplying the standard USB 5V and power management IC for the
applications processor. The power management IC provides the necessary reset and voltage
sequencing to start the processor correctly. The power management IC supplies the rest of the
circuits with 1.55V, 1.88V, 2.8V and 3.3V.
Moreover, 13.8V (A+) is fed to a MOSFET to supply 13.8V back to the transceiver power circuitry as
a sense line to turn ON or OFF the transceiver.
2.3.3
User Interface (Keypad, STN Display, Volume and Frequency Knob) section
2.3.3.1 Display
The control head assembly utilizes a Super Twisted Nematic (STN) Liquid Crystal Display (LCD) with
a dot-matrix resolution of 131x 53 pixels. The LCD is configured to display a row of eight
alphanumeric characters, eight soft icons and four soft menu keys. The LCD is controlled by the
applications processor through eight parallel LCD interface lines and operates off a 2.8V supply.
The trans reflective module comes with four yellow LEDs for backlighting and is capable of three
steps dimming together with the backlight LEDs, namely OFF, Low and High, driven by SW_B+ at
13.8V.
June 15, 2005
Product Overview: Control-Head Assembly
6815854H01-A
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