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20.3.3
Detection Frequency
The detection frequency have a detection frequency range and an undetectable frequency range because of
oscillation accuracy. Therefore, it is undefined whether to be detected between detection frequency range
and undetectable it.
Figure 20-2 shows the detection or undetectable frequency range when the target clock error is ±10% and
the reference clock error is ± 5%.
Subharmonic
(10MHz + 10%) ÷ 2
5.15
9
Figure 20-2 Example of detection frequency range (in case of 10MHz)
The higher and lower limit of the detection frequency is calculated from the maximum error of the target
clock and the reference.
How to calculate the setup value of OFDMN/OFDMX is shown below when the target clock error is
±10% and the reference clock error is ± 5%.
higher limit of the detection frequency
lower limit of the detection frequency
higher limit of the detection frequency
lower limit of the detection frequency
Setting "0x4A" to the register OFDMX and "0x37" to the register OFDMN, when the external oscillation
of higher than 11MHz or lower than 9MHz is detected, the oscillation frequency detector outputs a reset signal.
20.3.4
Available Operation Mode
The oscillation frequency detection is available only in NORMAL and IDLE mode. Before shifting to anoth-
er mode, disable the oscillation frequency detection.
Harmonic
(10MHz - 10%) * 2
9.5
10
10.5
11
target clock
10MHz ± 10%
(f
)
EHOSC
reference clock
10MHz ± 5%
(f
)
IHOSC
= 1 ÷ {(d ÷ 2
) ÷ (a ÷ 4)}
8
= 1 ÷ {(c ÷ 2
) ÷ (b ÷ 4)}
8
= 1 ÷ {(9.5 × 10
÷ 2
) ÷ (11 × 10
6
8
= 1 ÷ {(10.5 × 10
÷ 2
) ÷ (9 × 10
6
8
Page 429
f
[MHz]
19.4
EHOSC
Max.11MHz
--------
a
Min. 9MHz
--------
b
Max.10.5MHz
--------
c
Min. 9.5MHz
--------
d
÷ 4)}
= 74.10 = 74 (truncate after the decimal places)= 0x4A
6
÷ 4)}
= 54.85 = 55 (round up after the decimal places)= 0x37
6
TMPM3V6/M3V4
Detection range
Undetectable range
2019-02-06
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