AT91SAM7S256D-AU Atmel, AT91SAM7S256D-AU Datasheet - Page 197

• Manufacturer Part Number: AT91SAM7S256D-AU
• Description: ARM Microcontrollers - MCU 256K Flash SRAM 64K ARM based MCU
• Manufacturer: Atmel
• Series: SAM7S256r

Specifications of AT91SAM7S256D-AU

• Rohs: yes
• Core: ARM
• Processor Series: AT91SAM
• Data Bus Width: 16 bit/32 bit
• Maximum Clock Frequency: 55 MHz
• Program Memory Size: 256 KB
• Data Ram Size: 64 KB
• On-chip Adc: Yes
• Operating Supply Voltage: 3 V to 3.6 V
• Operating Temperature Range: - 40 C to + 85 C
• Package / Case: LQFP-64
• Mounting Style: SMD/SMT
• Interface Type: 2-Wire, I2S, SPI, USART
• Length: 7 mm

25.8
25.8.1
25.8.2
Clock Switching Details
Table 25-1
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.
Table 25-1.
Figure 25-3. Switch Master Clock from Slow Clock to PLL Clock
To
Main Clock
SLCK
PLL Clock
Master Clock Switching Timings
Clock Switching Waveforms
From
gives the worst case timings required for the Master Clock to switch from one selected clock to another
Clock Switching Timings (Worst Case)
Write PMC_MCKR
Master Clock
PLLCOUNT x SLCK +
Slow Clock
0.5 x Main Clock +
0.5 x Main Clock +
2.5 x PLLx Clock
PLL Clock
MCKRDY
Main Clock
4.5 x SLCK
4 x SLCK +
LOCK
–
PLLCOUNT x SLCK
2.5 x PLL Clock +
2.5 x Main Clock
4 x SLCK +
5 x SLCK +
SLCK
–
PLLCOUNT x SLCK
2.5 x PLL Clock +
SAM7S Series [DATASHEET]
3 x PLL Clock +
3 x PLL Clock +
1 x Main Clock
4 x SLCK +
4 x SLCK +
PLL Clock
5 x SLCK
6175M–ATARM–26-Oct-12
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