Sony SPP-930, Руководство по обслуживанию

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4.4.4 ATE Interface
All connections to the ATE jig are facilitated by a single 10-pin header rather than a bed of nail which has been shown to have
reliability problems. The ATE uses the header to access the signals required to complete a handset alignment. Handset to ATE
communication is accomplished through a dedicated port on the MCU which is connected directly to a charge contact. As with other
charge contacts the ATE I/O contacts are protected from ESD using LC filtering and additional protection is afforded at the MCU’s
port by using protection diodes.
4.4.5 Ringer
The ringer used in the handset is basically a magnetic transducer. It takes an electrical signal from the MCU and uses it to create a
varying magnetic field to vibrate a metal diaphragm. The vibrating diaphragm in turn produces acoustic waves forming sound
energy. The ringer draws a large amount of current when it rings and is therefore powered directly from the battery. There are four
different ring signals produced by the MCU to provide four distinct ringing tones. Each signal is a combination of two frequencies.
The frequencies are listed in Table 4.4.5.
Table 4.4.5 MCU Ringer Tone Frequencies
RING TONE NUMBER FREQUENCY #1 (Hz) FREQUENCY #2 (Hz)
l 2,500 1,250
2 2,500 625
3 1,250 625
4 312
The MCU’s ringing tones are coupled to the ringer via transistors. These transistors are biased to insure that ringer output is consis-
tent from handset to handset.
4.4.6 Sleep Timer
The sleep timer wakes up the handset from sleep mode by pulling the IRQ line on the MCU low. The sleep timer circuit is made up
of a compactor, an RC network and supporting components. The circuit acts basically like a one-shot activated by the RX_PWR line.
With the MCU asleep, the receive power is off allowing an RC network to charge up. The charge on the capacitor is compared to a set
reference and at a certain point toggles the comparator output low. The low pulls the IRQ low waking up the MCU.
When the MCU a wakes, it executes its interrupt routine to check for base data. To do this, the MCU powers the RX_PWR line which
in turn resets the IRQ line high. As soon as the MCU completes its interrupt routine, the handset goes back to sleep if no base data was
detected and the sequence is repeated.
4.4.7 LED Indicators
The handset features two LED indicators. One indicator is used to show that the handset is in use while the other indicates a low
battery condition. The low battery indicator is turned off and on by the MCU until either the battery reaches a charged state (> 3.35
VDC), or the handset is shut done do to insufficient battery charge (< 2.8VDC).