Panasonic EB-X700 Service Manual page 19

4.5.5. PCM Audio Routing to/from Application Processor & Bluetooth
Although the Modem handles the speech audio to and from the microphone and handset / hands-free loudspeakers, MP3-
decoding, voice-recognition, high-quality ring-tones and other synthesised audio are handled or generated by the Application
Processor. These are passed between the Modem and Application Processor via the dedicated digital PCM bus called
IPCAUDIO (Inter-Processor Communication - Audio). This is a 4 line bus (IPCAUD-CLK, IPCAUD-TX, IPCAUD-RX and
IPCAUDSYNC), with the Modem always being the IPCAUD Bus Master. Various sample rates are supported, depending upon
the quality of the audio, from 8kSamples/s to 48kSamples/s.
Bluetooth audio support is also provided by the separate, highly-integrated Bluetooth ASIC (U504). Audio at Samples/s is
passed between S-Gold and the Bluetooth ASIC in digital PCM format via PCM-CLK, PCM-IN, PCM-OUT and PCM- SYNC.
The Bluetooth ASIC is always the PCM Bus Master.
4.5.6. Subscriber Identity Module (SIM)
The Modem supports the SIM Card (Subscriber Identity Module) interface. The Power Management Sub-System has been
designed to provide 2.8 V or 1.8 V supplies to the SIM, although the software may only support 2.8 V SIMs. The power to the
SIM can be switched off by S-Gold's CC_VZ_N output, which allows additional power savings, while the rest of the Modem
remains powered-up and operational.
4.5.7. Power Supply and Battery Management (inc. Charging)
The Modem handles the battery charging algorithm, which is started when a charger is inserted into the handset. It also provides
an indication of the battery voltage (and hence an estimate of the remaining capacity) for display to the User. It automatically
switches between fast charging and trickle charging (battery full maintenance).
4.5.8. PWM Generation (Main & Sub-Display Backlights & Photolight)
Since S-Gold incorporates a set of Capture-Compare (CAPCOM) functions, these are utilised to produce Pulse-Width-
Modulated digital logic-level outputs, each with a variable duty-cycle. These outputs can be used to vary the intensity of the LCD
backlights, and operate at a high frequency with an increasing proportion of the time at a high logic level corresponding to an
increased drive provided to each respective backlight:
The PWM signal controlling the brightness of the Main LCD backlight is provided by CC1CCIO4;
The PWM signal controlling the brightness of the Sub LCD backlight is provided by CC1CCIO0;
The PWM signal controlling the brightness of the Camera Photo-light is provided by CC1CCIO2.
The camera photolight is provided in the handset so that images may be captured at low light levels. The Photolight drive level
is variable so that the appropriate amount of illumination may be selected for the best quality low-light image capture.
4.5.9. IPC Communication
The Modem and Application Processor systems communicate via the asynchronous serial IPC-PRIMARY bus (Inter-Processor
Communication - Primary), over lines IPCPRI-TX, IPCPRI-RX, IPCPRI-RTS and IPCPRI-CTS.
4.5.10. Application Processor Clock, Reset & Hand-shaking
In the EB-X700 architecture, the Modem is responsible for providing the Application Processor with a 13 MHz clock, and the
necessary reset and 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 handshaking mechanism is provided to allow the Application Processor to signal to the Modem that it no longer requires the
13 MHz clock (via line AP-CLK-REQ), allowing the Modem to switch-off the VCTCXO for power-saving, if the Modem also does
not require the system clock.
A further hand-shaking 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.
– 4-8 –
PROVISIONAL ISSUE