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4.4.
Baseband Overview
4.4.1
Introduction
The X700 architecture consists of two main sections; a GSM Modem to handle the speech coding and air interface protocol,
and an Applications Processor to provide the MMI, peripherals support and to execute software applications. Here the GSM
Modem is described, also commonly known as the Baseband section:
The functionality of the GSM Modem is primarily implemented by the Infineon S-Gold ASIC (PMB8870), supported by the
Infineon Power Management IC (PMIC) called S/M-Power (PMB86811), with functionality extended by the Panasonic
Companion IC (AN32061A). The PMIC and the Companion IC are discussed separately in a later section.
S-Gold's Baseband circuits in the X700 architecture perform the following functions:
GSM Channel Equalization
• GSM Channel Coding / Decoding
• Speech Coding / Decoding
• GPRS (Packet) Support
• Data Encryption
• Basestation Synchronization & Frequency Locking (AFC)
• RF Scheduler and Transmit Power Control
• Real Time Clock (for Day/Date & Idle-Mode Power Saving)
• Audio and Tone Synthesis/Generation (except Ring-Tones, Music & Audio Samples)
• PCM Audio Routing to/from Application Processor & Bluetooth Module
• SIM Interface and Management
• Power Supply and Battery Management (including Charging)
• PWM Generation (Control of the Main & Sub-Display Backlights, and Camera Photolight Intensity)
• IPC Communication with the Application Processor (running the Man-Machine Interface)
• Provision of Application Processor 13MHz Clock, Reset and Handshaking Signals
• Miscellaneous Support (Clamshell Flip Sensor, Headset Detect & HS Send/End, Battery Temperature)
The GSM Modem (S-Gold) can be viewed as a module, performing the aforementioned tasks, generally under the control of
the Application Processor. S-Gold executes its own locally stored code from 4MB of Flash, with 1MB of SRAM provided in a
stacked Flash & RAM package to save PCB area. S-Gold receives instructions at UART1 from the ApplicationProcessor
via the Primary Inter-Processor Communication (IPC-PRIMARY) serial link. The Application Processor is discussed
separately.
At phone power-up, S-Gold boots from its external Flash memory, initializes the Modem as a whole into an idle state,
and supplies the divided-by-2 system clock to the Application Processor, which then boots-up after reset is released by S-Gold.
Once the Application Processor has booted, it then takes overall control of the entire system.
PROVISIONAL ISSUE
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