
PEB 20560
Functional Block Description
Semiconductor Group
2-120
2003-08
2.12.2
Types of Clock Signals
2.12.2.1
Input/Output Clocks
CLK16: 16.384 MHz VCXO clock voltage oscillator
CLK61: 61.44 MHz ext. oscillator clock
CLK40-XI: up to 40 MHz ext quartz clock
CLK40-XO: up to 40 MHz ext quartz clock
CLK30: 30.72 MHz (i.e. for
μ
P)
CLK15: 15.36 MHz (i.e. for OCTAT-P)
CLK7: 7.68 MHz (i.e. for QUAT-S)
PFS: Frame synchronization on PCM 8 kHz
PDC2: PCM data clock 2.048 MHz
PDC4: PCM data clock 4.096 MHz
PDC8: PCM data clock 8.192 MHz (i.e. for FALC54)
FSC: Frame synchronization on IOM-2 interface 8 kHz
DCL: IOM-2 data clock
XCLK: 8 kHz or 512 kHz or 1.536 MHz or 2.048 MHz (selectable) input
REFCLK (i.e. 512 kHz)
input
input
input
output
output
output
output
input/output
input/output
input/output
input/output
input/output
input/output
input/output
2.12.2.2
Clock Selection
DSP clock: Selectable clock ~ 20, 30 or 40 MHz
– The DSP clock can be selected from 3 possible frequencies: 20, 30 or 40 MHz.
– The source of the clock can be one of two:
61.44 MHz external oscillator, which by dividing by 2,3 produces the 20, 30 MHz
clock 40 MHz crystal with an internal oscillator which produces the 40 MHz clock.
– DSP clock frequency is determined by the input pins, FREQ1…0. The value of
these pins can be read from CCSEL0 register, bits1…0 (read only bits).
RTCLK: Real time clock
– Clock for Real Time Interrupt: 1 Hz (1 s) or 100 Hz (10 ms)
– The RTC interrupt is a periodic interrupt activated every 10 ms/1 s and it is
programmable via CCSEL1:RTCP.
Programmable UART clock
– The UART clock is CLK61 divided by 5. It can be further divided by programming
the UART. (For more details see
Table 2-34
in
section 2.14.1.2
)
PFS: Frame synchronization on PCM 8 kHz
– The PFS signal can be derived from either the CLK16 input clock or be driven by
an external signal via the IO pads. The selection between external and internal
signals is performed by CCSEL0:MS (master/slave bit). See
Figure 2-46
.
internal clock
internal clock
internal clock
input/output