CC2430 Datasheet, PDF (70/212 Pages) Texas Instruments – A True System-on-Chip solution for 2.4 GHz IEEE 802.15.4 / ZigBee-TM

CC2430
Peripherals : Power Management and clocks
therefore the calibration may be disabled by
setting register bit SLEEP.OSC32K_CALDIS
to 1. Note that any ongoing calibration will be
completed when a 1 is written to
SLEEP.OSC32K_CALDIS.
13.1.4.4
Oscillator and Clock Registers
This section describes the Oscillator and Clock
registers. All register bits retain their previous
values when entering PM2 or PM3 unless
otherwise stated.
CLKCON (0xC6) – Clock Control
Bit Name
7 _OSC32K
Reset R/W
1
R/W
6 _OSC
1
R/W
5:3 TICKSPD[2:0] 001 R/W
2:1 _-
0 _CLKSPD
00
R
1
R
Description
32 kHz clock oscillator select. The 16 MHz high frequency RC
oscillator must be selected as system clock source when this bit is
to be changed.
0 – 32.768 kHz crystal oscillator
1 – 32 kHz RC oscillator
Note: this bit is not retained in PM2 and PM3. After re-entry to PM0
from PM2 or PM3 this bit will be at the reset value 1.
System clock oscillator select:
0 – 32 MHz crystal oscillator
1 – 16 MHz high frequency RC oscillator
This setting will only take effect when the selected oscillator is
powered up and stable. If the XOSC oscillator is not powered up, it
should be enabled by SLEEP.OSC_PD bit prior to selecting it as
souorce. Note that there is an additional wait time (64 µs) from
SLEEP.XOSC_STB set until XOSC can be selected as source. If
RC osc is to be the source and it is powered down, setting this bit
will turn it on.
Timer ticks output setting, can not be higher than system clock
setting given by OSC bit setting
000 – 32 MHz
001 – 16 MHz
010 – 8 MHz
011 – 4 MHz
100 – 2 MHz
101 – 1 MHz
110 – 500 kHz
111 – 250 kHz
Reserved.
Clock Speed. Indicates current system clock frequency. The value
of this bit is set by the OSC bit setting
0 – 32 MHz
1 – 16 MHz
This bit is updated when clock source selected with the OSC is
stable
13.1.5 Timer Tick generation
The power management controller generates
a tick or enable signal for the peripheral
timers, thus acting as a prescaler for the
timers. This is a global clock division for Timer
1, Timer 3 and Timer 4. The tick speed is
programmed from 0.25 MHz to 32 MHz in the
CLKCON.TICKSPD register. It should be noted
that TICKSPD must not be set to a higher
frequency than system clock.
13.1.6 Data Retention
In power modes PM2 and PM3, power is
removed from most of the internal circuitry.
However parts of SRAM will retain its
contents. The content of internal registers is
also retained in PM2 and PM3.
The XDATA memory locations 0xF000-
0xFFFF (4096 bytes) retains data in PM2 and
PM3. Please note the exception as given
below.
The XDATA memory locations 0xE000-
0xEFFF (4096 bytes) and the area 0xFD56-
CC2430 Data Sheet (rev. 2.1) SWRS036F
Page 70 of 211