PXD20RM Datasheet, PDF (230/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

Bit 16
Bits 17-18
Bits 19-23
Bit 24
Bits 25-29
Bit 30
Bit 31
Table 8-21. OSC_CTL field descriptions
M_OSC: Crystal oscillator clock interrupt mask
0: Crystal oscillator clock interrupt is masked.
1: Crystal oscillator clock interrupt is enabled.
Reserved
OSCDIV[4:0]: Crystal oscillator clock division factor
These bits specify the crystal oscillator output clock division factor. The output clock is divided by the
factor OSCDIV+1.
I_OSC: Crystal oscillator clock interrupt
This bit is set by hardware when OSCCNT counter reaches the count value EOCV[7:0]*512. It is
cleared by software by writing ‘1’.
0: No oscillator clock interrupt occurred.
1: Oscillator clock interrupt pending.
Reserved
S_OSC: Crystal oscillator statusl
0: Crystal oscillator output clock is not stable.
1: Crystal oscillator is providing a stable clock.
OSCON: Crystal oscillator powerdown control
0: Crystal oscillator is switched off.
1: Crystal oscillator is switched on.
Note: OSC_CTL register is writable only in supervisor mode.
8.4.3 SIRC digital interface
8.4.3.1 Introduction
The SIRC digital interface controls the internal low power 128 kHz RC oscillator (SIRC). It holds control
and status registers accessible for application.
8.4.3.2 Slow Internal RC Oscillator (128 kHz)
The SIRC provides a low frequency (f_SIRC) clock in the range of tens of kHz requiring less current
consumption. This clock can be used as reference clock when a fixed base time is required for specific
modules.
The SIRC is always on in all device modes.
The SIRC clock can be further divided by a configurable division factor in the range 1 to 32 to generate
the divided clock to match system requirements. This division factor is specified by the LPRCDIV[4:0]
bits of SIRC_CTL register.
After a power-on reset, the SIRC is trimmed using a factory test value stored in test flash memory.
However, after a power-on reset the test flash memory value is not visible at SIRC_CTL[LPRCTRIM] and
this field shows a value of zero. Therefore, one should be aware that the SIRC_CTL[LPRCTRIM] does
not reflect the current trim value until someone has written to this field. Particular attentionshould be paid
to this feature when a read-modify-write operation is initiated on SIRC_CTL, because a SIRCTRIM value
8-34
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
Freescale Semiconductor