Motorola APX 5000 Service Manual page 53

Basic Theory of Operation: Controller Section Sec 1: 3-11
The ARM controller core of the OMAP processor handles the power up sequence of all devices,
including firmware upgrades, and all operating system tasks that are associated with FLASH and
SDRAM memories and user interface communication. The FLASH memory (64 MB) is required to
store the firmware, tuning, and Codeplug settings, which upon initialization get read and stored into
SDRAM (32 MB) for execution. The ARM and DSP core jointly control and configure audio, wireless
and RF devices linked to the Serial Peripheral Interface (SPI) and Synchronous Serial Interface
(SSI) buses to enable radio FM and optional wireless communication protocols. For encryption, a
separate ARM processor is used (MACE) to encode and decode encryption packets coming in from
the main OMAP processor through the SSI interface. Its firmware is flashed via the main processor
during an upgrade request to its internal FLASH memory. The MACE encryption processor is located
on the expansion board.
The power and most clocks to the controller devices are provided by the MAKO IC and external
switching and linear regulators on board. A Complex Programmable Logic Array (CPLD) IC divides
the 24.576 MHz clock from MAKO to source OMAP's 32 kHz Real Time Clock, and MACE's 4 MHz
main clock. OMAP's main clock is supplied externally from an on board 12 MHz crystal.
The radio has two internal microphones and an internal speaker, as well as available microphone
and speaker connections for external accessories. The internal 4 Ohm speaker is located opposite to
the main display and keypad of the radio. The internal speaker is driven by a Class D audio amplifier
located on the expansion board that is capable of delivering a rated power of 0.5 W. The external
accessory speaker is driven by a Class AB audio amplifier on the MAKO IC that is capable of
delivering 0.5 W of power into a 16 Ohm load. Both speaker paths use the CODEC for volume
control and to convert the audio signal from digital to analog. Both internal and external microphones
use the CODEC's ADC to deliver digital audio samples to the DSP controller.
The user interface block consists of a top and main or "data side" display, a keypad, top controls and
the accessory side connector. The side connector (Universal Connector) provides audio, USB,
RS232 and RF communication for accessories. All signals to and from the connector go through the
internal expansion board before reaching the microcontroller and other devices on the main board.
3.4.1 Radio with Mace with Apps Expansion Board
In addition to the Mace Expansion Board features, the Mace with Apps Expansion Board consists of
an e-MMC 4GB NAND Flash, a 3-axes digital accelerometer, and an integrated-circuit consisting of a
Global Positioning System (GPS) and Bluetooth 2.1 transceiver. The 4GB external NAND Flash
communicates to the OMAP processor on the VOCON board through the Multi Media Card (MMC)
interface. The GPS receiver section of the GPS/BT combination IC interfaces with the OMAP
processor though a dedicated UART port. The GPS receiver also has a dedicated reset controlled
solely by the OMAP processor.
The radio also has the ability to connect to a wireless Bluetooth audio headset. This feature is
implemented using a combination Bluetooth/GPS integrated circuit (IC) located on the expansion
board. An optional accessory headset can connect using a low-data rate GFSK modulated signal
hopping on 79 x 1 MHz wide Bluetooth channels from 2402 MHz to 2480 MHz in the ISM band. Each
APX accessory that is capable of Bluetooth communication will have its own unique Bluetooth
address. Bluetooth uses a frequency hopping spread spectrum (FHSS) technique to spread the RF
power across the spectrum to reduce the interference and spectral power density. The frequency
hopping allows the channel to change up to 1600 times a second (625 μs time slot) based on a
pseudo random sequence. If a packet is not received on one channel, the packet will be
retransmitted on another channel. The Bluetooth IC sends data to the AVR32 processor that is also
located on the expansion board over an HCI UART link. The AVR32 processor communicates to the
OMAP processor on the VoCon board through a dedicated USB port.