CMS32L051 User Manual |Chapter 4 Clock Generation Circuit
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4.7 High-speed internal oscillation correction
4.7.1 High-speed internal oscillation self-adjustment function
This function measures the frequency of high-speed internal oscillators with the subsystem clock fSUB
(32.768KHz) and corrects the frequency accuracy of high-speed internal oscillators fHOCO in real time.
Table 4-9 shows the operation specifications of high-speed internal frequency correction function, and
Figure 4-18 shows the block diagram of high-speed internal frequency correction function.
Table 4-9 Operating specifications for the high-speed internal oscillation frequency correction function
fSUB/2
9
(subsystem clock 32.768KHz).
fHOCO (fast inner swing)
Continuous Operation mode
A mode of continuous high-speed internal vibration frequency correction
Interval Operation mode
A mode of high-speed internal frequency correction is spaced by using a timer clock end,
etc
Clock accuracy
adjustment function
Correction time: Correction period (31.2ms) X (correction number -0.5)
Note
Interrupt when high-speed internal oscillation frequency correction is complete (when
interrupt permission is on)
Note: Correction time: Varies depending on the number of corrections.
Correction period: The total time of the frequency determination phase and the frequency correction
phase.
Number of corrections: The number of corrections in which the frequency is bundled to the expected
range.
Figure 4-18 High-speed internal vibration frequency correction function
20 bit counter
Frequency
dividing circuit
Expected
value
circuit
Comparis
on circuit
Correction value [6:0]
CPU bus
Counter start
(CRCTL register: CRST bit)
fSUB/2^9
fSUB
(The counter starts to trigger)
Counting clock
fHOCO
Decrement
signal
Incremental
signal
SubOSC
32.768KHz
Clock correction
FRQSEL4-3
High speed internal
vibration correction
completion interrupt
（INTCR）
Option
Bytes
00C2H
High speed internal
vibration
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