Freescale Semiconductor MCF52210, MCF52211, MCF52212, MCF52213 6.7.1.3 Relaxation Oscillator Control Register (ROCR), 6.7.1.4 Low-Power Divider Register (LPDR)

Clock Module
MCF52211 ColdFire® Integrated Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor 6-11
6.7.1.3 Relaxation Oscillator Control Register (ROCR)
The ROCR is used to trim the frequency of the on-chip oscillator. Setting one of the TRIM bits engages
its associated bypass capacitance, which increases or decreases the period of the output frequency. The
largest capacitance, and thus the biggest frequency step (40%), is associated with TRIM9. The lowest
capacitance, and thus the smallest frequency step (0.8%), is associated with TRIM0. The tuning steps are
binary-weighted in terms of signal period, not frequency. The module was designed such that the
approximate middle of the tuning range is 8 MHz.
6.7.1.4 Low-Power Divider Register (LPDR)
The LPDR contains a 4-bit field that divides down the system clock (regardless if the reference clock or
PLL clock is driving the system clock) by a factor of 2n (where n is a number from 0 to 15 represented by
the 4 bit field). The clock change takes effect with the next rising edge of the system clock.
IPSBAR
Offset: 0x12_0004 (ROCR)
Access: Supervisor read/write
15 14 13 12 11 10 9 8
R——————TRIM9TRIM8
W
Reset000000See note
1
1Loaded during reset from the flash information row (bits [9:0]).
See note 1
76543210
R TRIM7 TRIM6 TRIM5 TRIM4 TRIM3 TRIM2 TRIM1 TRIM0
W
Reset See note 1 See note 1 See note 1 See note 1 See note 1 See note 1 See note 1 See note 1
Figure 6-4. Relaxation Oscillator Control Register (ROCR)
Table 6-7. ROCR Field Descriptions
Field Description
15–10
—
Reserved, should be cleared.
9–0
TRIM
10-bit trim value used to trim the frequency of the on-chip oscillator.
IPSBAR
Offset: 0x12_0007 (LPDR)
Access: Supervisor read/write
76543210
R————
LPD3 LPD2 LPD1 LPD0
W
Reset:00000000
Figure 6-5. Low-Power Divider Register (LPDR)