Atmel SAM9X25, Manual

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11054A–ATARM–27-Jul-11
SAM9X25
188
11054A–ATARM–27-Jul-11
SAM9X25
Peripheral clock 4 is disabled.
22.12 Clock Switching Details
22.12.1 Master Clock Switching Timings
Table 22-1 and Table 22-2 give the worst case timings required for the Master Clock to switch
from one selected clock to another one. This is in the event that the prescaler is de-activated.
When the prescaler is activated, an additional time of 64 clock cycles of the new selected clock
has to be added.
Notes: 1. PLL designates either the PLLA or the UPLL Clock.
2. PLLCOUNT designates either PLLACOUNT or UPLLCOUNT.
Table 22-1. Clock Switching Timings (Worst Case)
From Main Clock SLCK PLL Clock
To
Main Clock –
4 x SLCK +
2.5 x Main Clock
3 x PLL Clock +
4 x SLCK +
1 x Main Clock
SLCK
0.5 x Main Clock +
4.5 x SLCK
–
3 x PLL Clock +
5 x SLCK
PLL Clock
0.5 x Main Clock +
4 x SLCK +
PLLCOUNT x SLCK +
2.5 x PLLx Clock
2.5 x PLL Clock +
5 x SLCK +
PLLCOUNT x SLCK
2.5 x PLL Clock +
4 x SLCK +
PLLCOUNT x SLCK
Table 22-2. Clock Switching Timings between Two PLLs (Worst Case)
From PLLA Clock UPLL Clock
To
PLLA Clock
2.5 x PLLA Clock +
4 x SLCK +
PLLACOUNT x SLCK
3 x PLLA Clock +
4 x SLCK +
1.5 x PLLA Clock
UPLL Clock
3 x UPLL Clock +
4 x SLCK +
1.5 x UPLL Clock
2.5 x UPLL Clock +
4 x SLCK +
UPLLCOUNT x SLCK