Panasonic EBX70 - CELL PHONE, Service Manual

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TECHNICAL DESCRIPTION
Issue 1 Section 4 PMCD030901C8
Revision 0 – 14 – Service Manual
The Baseband circuits are built around a GSM chipset developed by Texas Instruments. The chipset comprises two chips,
and SYREN. The highly integrated nature of the chips means that each contain a large number of functions.
is a signal processing device with a digital signalling processor (DSP) and CPU. The DSP performs channel and
speech encoder/decoder tasks, together with equalisation and encryption. The CPU runs layer 1, 2, and 3 software, controls
the MMI, SIM and system interfaces, real time clock, and battery and power management. also controls SYREN.
SYREN provides frame timing, A/D conversion, RF power control, audio interfacing including tone generation, and baseband
power supplies.
4.4.2 Keypad
The keyboard interface supports keypads up to 6 columns by 6 rows and has a built-in scanning algorithm for hardware-
based key press decoding. Four key press detection modes are offered: matrix, allowing 25 keys to be scanned. When a key
being pressed, a keypad interrupt is generated. To find which key has been pressed, the software scans each column in turn
and reads which row is active. Because of key bounce, the key press is confirmed twice at approximately 20 ms intervals.
• Event detection on both key press and key release.
• Programmable press detection on key release only.
• Long key detection on prolonged key press.
• Time out on permanent key press or after keyboard release.
Figure 4.6: Keypad Connections
The controller supports detection of single and multiple key presses. On a key press or key release, and allowing for
debounce time, the scanning sequencer is activated. The resulting digital snapshot of the keypad is registered and compared
to the previous one. On change detection, an interrupt is sent to the MCU.
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