Panasonic EB-X700 Service Manual page 20

4.5.11. Miscellaneous Support
The Flip Sensor (U400) is a magneto-resistive device which changes its output logic level in the presence of a magnetic field.
When the clamshell is closed, a magnet in the upper part of the handset aligns with U400 mounted on the main PCB, causing
the logic level to change to High. This is sensed by S-Gold at KP-IN4, and this information is relayed to the Application
Processor to switch off the Main LCD and its backlight to save power (while switching on the Sub-LCD), as well causing the
S-Gold to disable the handset audio circuits to prevent acoustic feedback. Note that S-Gold's keypad interface function is not
used, and instead purely functions as General-Purpose Input/Output (GPIO).
Insertion or removal of a personal Handsfree (ear-bud & microphone) is detected by S-Gold via a logic level change on HSDET.
This accessory incorporates a headset cord-mounted switch, which when pressed shorts HS-SEND/END to ground, signalling
to S-Gold that a call is to be answered or ended, as appropriate.
S-Gold also has an internal analogue-to-digital conversion block. This is used for a number of analogue sensing functions,
such as charge current monitoring (for charging status detection), battery temperature monitoring (for safety), and RF system
temperature monitoring (for calibration adjustment for accuracy).
4.5.12. Modem Memories
The Modem has dedicated non-volatile NOR Flash and volatile asynchronous SRAM memories, separate from the
Application Processor memories. The Flash is needed to retain and execute the Modem software, which is primarily used
to control Modem reception and transmission across the RF air interface.
Upon initial power-up of the Modem, S-Gold boots from an internal boot memory, determining whether to continue to boot
from the external Flash for normal handset operation, or whether to initiate re-programming.
Both the individual Flash and SRAM silicon die are located in a single stacked Multi-Chip Package (MCP) in order to
save PCB area, with the (joint) component designation U102. The MCP is organised as 32 Mbits of Flash (2M address
locations x 16 bits wide data) plus 8Mbits SRAM (512k locations x 16 bits wide data). The Flash supports 52MHz burst
operation for speed. Both memories operate at 1.8 V for low power.
4.6. Baseband Overview (Application Processor)
4.6.1. AT Command Communication with GSM Modem S-GOLD
The Application Processor and Modem processor communicate via the asynchronous serial IPC-PRIMARY bus (Inter-
Processor Communication - Primary), over lines IPCPRI-TX, IPCPRI-RX, IPCPRI-RTS and IPCPRI-CTS, a part of IPC
communication link. AT commands are transferred between two processors to link the smart phone software running on
the application processor side with the Modem software running on the Modem processor side.
4.6.2. PCM Audio Routing to/from S-GOLD
In the EB-X700 architecture design, the Modem is responsible for providing the Application Processor with a 13 MHz
clock, and the necessary reset control handshaking signals. At initial power-up, the Modem (S-Gold) boots itself, while
holding the Application Processor in reset. After a short time, the Modem provides the 13 MHz clock to the Application
Processor, and releases the reset line (AP-RST). The Application Processor then boots, and assumes control of the
handset (including the Modem).
A reset handshaking mechanism is provided for the Application Processor to signal to the Modem that an error and
reset event occurred in the Application Processor, requiring an overall system reset to recover (via line AP-WAS-RST).
This allows the handset to take the appropriate automatic reset and reboot action necessary to return functionality to
the User.
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PROVISIONAL ISSUE