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Chapter 50 Subclock Calibration Unit
4.Clocks
4. Clocks
The module operates with 3 different clocks: The 4 MHz clock OSC4, the 32 kHz clock OSC32 (ot the 100kHz
clock OSC100) and the peripheral clock CLKP. Synchronization circuits adapt the different domains.
The clock frequencies have to fulfill the following requirements:
● Clock ratio
T
OSC32/OSC100
> 2 x T
OSC4
+ 3 x T
CLKP
T
OSC4
< 1/2 x T
OSC32/OSC100
- 3/2 x T
CLKP
T
CLKP
< 1/3 x T
OSC32/OSC100
- 2/3 x T
OSC4
● The input frequencies must not exceed the values given in Table 4-1 .
Table 4-1 Maximum operation frequencies
Table 4-2 Example of valid clock ratios which fulfill requirements 1 and 2
OSC32/OSC100 OSC4 CLKP
maximum 2 MHz 500 ns 10 MHz 100 ns 50 MHz 20 ns
OSC32 OSC100 OSC4 CLKP
maximum operation
speed
2 MHz 500 ns 2 MHz 500 ns 10 MHz 100 ns 50 MHz 20 ns
normal operation 32 kHz 31.25 us 100 kHz 10 us 4 MHz 250 ns >2 MHz 500 ns