Panasonic EB-X700 Service Manual

Also see for EB-X700: Operating instructions

– 4-7 –4.5.3. Real Time Clock (RTC)The Real Time Clock block (located inside S-Gold) performs several functions. It is used to time the intervals between pagingslots when the handset is otherwise shut-down, to save power, and also to maintain the current date and time. Since the RTCBlock is clocked by its own low frequency (32,768 Hz) crystal, it consumes very little power, and is relied upon to keep trackof elapsed time whenever the handset is in power saving mode (when the main 26 MHz VCTCXO is switched-off).Prior to being used to accurately time successive paging slots, it is calibrated against the very accurate 26 MHz VCTCXO to± 1 count (± 1/32768 s), thus allowing a low-cost low-accuracy crystal to accurately time short intervals.The Power Management sub-system (discussed separately) incorporates a small 3V battery (button-type cell) which is keptcharged to allow the RTC to continue to maintain the current date and time during recharging or replacement of the mainhandset battery. A 2.1 V regulator then provides a constant voltage to the RTC Block, with the 3V battery voltage providingsufficient headroom for the battery to discharge over while providing the required RTC back-up time.4.5.4. Audio & Tone Synthesis/GenerationThe DSPs inside S-Gold also generate the DTMF (Dual-Tone-Multi-Frequency) signalling tones used to communicate overthe air interface with the POTs network or other equipment, in addition to performing voice encoding & decoding, andchannel encoding & decoding.The Modem S-Gold also incorporates an analog audio block, which provides an analog electrical interface for connectingthe microphone, speakers and headset to. Note that the audio transducers are actually indirectly connected via the PowerManagement Block, since this allows multiple audio transducers to be multiplexed to S-Gold, and for the signals to thespeakers to be buffered and amplified.T_OUT0 TX_ON_PA TX Power AmpOn/Off ControlT_OUT1 TX_ON_DRV Alternate source forDriver Enable,primary source isSmartiDC+.T_OUT2 VC1 Antenna Switch Control 1.T_OUT3 VC2 Antenna Switch Control 2.T_OUT4 VC3 Antenna Switch Control 3.T_OUT5 Not currently connected.T_OUT6 (R) (MODE) Future use for EDGE. Reserved - Not currently connected.T_OUT7 BAND_SELECT Alternate source forBand Select, primarysource is SmartiDC+.T_OUT8 (R) (TX-EDGE) Future use for EDGE. Reserved - Not currently connected.T_OUT9 Not currently connected.T_OUT10 Not currently connected.T_OUT11 BT_CLK_REQ Used as GPIO for When BT module powers up, thePull Up. BT_CLK_REQ is an input with weak pulldown.This PU is needed to provide theclock to BT module to boot-strap the clockenable. Used as a GPIO function only.T_OUT12 (R) (CRAM_MODE) Future use for CRAM GPIO function – not currently connected.mode selection.System Timer Signal Name Description Notes4.5.2. RF Scheduler and Transmit Power ControlS-Gold has a GSM System Interface Block which incorporates in hardware a GSM Timer which is programmed by the Modemsoftware to activate sections of the RF sub-system when required for reception during the paging channel timeslots, and an RFRamp Controller which additionally switches-on and ramps-up the transmit RF power amplifier when in a voice call sendingdata packets. By only activating the necessary parts of the system when required, battery life is extended considerably.The table below shows how these circuits are connected: