SAM7SE256 Atmel Corporation, SAM7SE256 Datasheet - Page 273

• Manufacturer Part Number: SAM7SE256
• Manufacturer: Atmel Corporation

Specifications of SAM7SE256

• Flash (kbytes): 256 Kbytes
• Pin Count: 144
• Max. Operating Frequency: 48 MHz
• Cpu: ARM7TDMI
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 88
• Ext Interrupts: 88
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 1
• Twi (i2c): 1
• Uart: 3
• Ssc: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 384
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 32
• Self Program Memory: NO
• External Bus Interface: 1
• Dram Memory: sdram
• Nand Interface: Yes
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8/3.3
• Operating Voltage (vcc): 3.0 to 3.6
• Fpu: No
• Mpu / Mmu: Yes / No
• Timers: 3
• Output Compare Channels: 3
• Input Capture Channels: 3
• Pwm Channels: 4
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: No

28.3.5
28.4
28.4.1
6222F–ATARM–14-Jan-11
Divider and PLL Block
Main Oscillator Bypass
PLL Filter
Slow Clock, so that the frequency of the crystal connected on the Main Oscillator can be
determined.
The user can input a clock on the device instead of connecting a crystal. In this case, the user
has to provide the external clock signal on the XIN pin. The input characteristics of the XIN pin
under these conditions are given in the product electrical characteristics section. The program-
mer has to be sure to set the OSCBYPASS bit to 1 and the MOSCEN bit to 0 in the Main OSC
register (CKGR_MOR) for the external clock to operate properly.
The PLL embeds an input divider to increase the accuracy of the resulting clock signals. How-
ever, the user must respect the PLL minimum input frequency when programming the divider.
Figure 28-3
Figure 28-3. Divider and PLL Block Diagram
The PLL requires connection to an external second-order filter through the PLLRC pin.
28-4
Figure 28-4. PLL Capacitors and Resistors
Values of R, C1 and C2 to be connected to the PLLRC pin must be calculated as a function of
the PLL input frequency, the PLL output frequency and the phase margin. A trade-off has to be
found between output signal overshoot and startup time.
shows a schematic of these filters.
shows the block diagram of the divider and PLL block.
MAINCK
SLCK
C2
Divider
DIV
C1
R
PLLRC
GND
PLLCOUNT
Counter
PLLRC
PLL
MUL
PLL
PLL
OUT
SAM7SE512/256/32
LOCK
PLLCK
Figure
273