Clock Module
MCF52211 ColdFire® Integrated Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor 6-13

6.7.1.7 Oscillator Control High Register (OCHR)

The OCHR is used to enable and configure the relaxation oscillator.

IPSBAR
Offset: 0x12_0009 (CCLR)
Access: Supervisor read/write
76543210
R————— — OSCSEL1 OSCSEL0
W
Reset:0000000See note
1
1The OSCSEL reset state is determined during reset configuration.

Figure 6-7. Clock Control Low Register (CCLR)

Table 6-10. CCLR Field Descriptions

Field Description
7–1 Reserved, should be cleared.
1
OSCSEL1
Oscillator Select 1 bit. This bit works in conjunction with the OSCSEL0 bit to select the clock source for the
PLL input/bypass clock, as shown in Table 6-1 1 .
0 PLL input/bypass clock comes from the external oscillator.
1 PLL input/bypass clock comes from the relaxation oscillator.
Note: When switching clock sources, the module ensures that, during the changeover, no spurious glitches
occur in the system clock, and that the crystal and relaxation oscillators remain enabled.
0
OSCSEL0
Oscillator Select 0 bit. This bit works in conjunction with the OSCSEL1 bit to select the clock source for the
PLL input/bypass clock, as shown in Tabl e 6-1 1 .
0 PLL input/bypass clock comes from the primary oscillator.
1 PLL input/bypass clock comes from the relaxation oscillator.
Note: When switching clock sources, the module ensures that, during the changeover, no spurious glitches
occur in the system clock, and that the crystal and relaxation oscillators remain enabled.

Table 6-11. CCLR[OSCSEL1] and CCLR[OSCSEL0] Settings

OSCSEL1 OSCSEL0 Source of PLL input/bypass clock
0 0 Primary oscillator (default)
0 1 Relaxation oscillator
10
Secondary oscillator
11