Clock Generation - Motorola V975 Service Manual

Theory of Operation
Baseband Electrical (Digital)

Clock Generation

PCAP can generate a 32kHz clock either from an in-
ternal RC Oscillator or an external crystal. The internal
RC oscillator doesn't provide the stability that the Rain-
bow requires for optimal performance, therefore, an
external 32.768kHz crystal is used.
Figure 3-24. RTC Clock
PCAP
RC
Oscillator
Xtal1
32kHz
Oscillator
Xtal2
The PGM2 pin of PCAP is tied to LCELL_BYP, to
prevent the internal RC oscillator from being routed to
the 32kHz pin under any circumstances. The 32kHz
oscillator will run at all times. It is powered by LCELL,
a coincell battery that is also used to maintain the real
time clock. The phone will only power up when the
32kHz becomes stable.
3-18
Debounce
Logic
8x PLL
Control
Logic
Clock
Detect
32kHz
32out_en
Motorola Confidential Proprietary
V975/V980
Draft 1.0