ATMEGA1284PR212-MU Atmel, ATMEGA1284PR212-MU Datasheet - Page 37

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ATMEGA1284PR212-MU

Manufacturer Part Number
ATMEGA1284PR212-MU
Description
BUNDLE ATMEGA1284P/RF212 QFN
Manufacturer
Atmel
Datasheet

Specifications of ATMEGA1284PR212-MU

Frequency
2.4GHz
Modulation Or Protocol
802.15.4 Zigbee, 6LoWPAN, ISM
Data Interface
PCB, Surface Mount
Memory Size
128kB Flash, 4kB EEPROM, 16kB RAM
Antenna Connector
PCB, Surface Mount
Package / Case
44-QFN, 32-QFN
Processor Series
ATMEGA128x
Core
AVR8
Data Bus Width
8 bit
Program Memory Type
Flash
Program Memory Size
128 KB
Data Ram Size
16 KB
Development Tools By Supplier
ATAVRRZ541, ATAVRRAVEN, ATAVRRZUSBSTICK, ATAVRISP2, ATAVRRZ201
For Use With
ATSTK600 - DEV KIT FOR AVR/AVR32
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Voltage - Supply
-
Power - Output
-
Operating Temperature
-
Applications
-
Sensitivity
-
Data Rate - Maximum
-
Current - Transmitting
-
Current - Receiving
-
Lead Free Status / Rohs Status
 Details
ATmega1284P
neither the clock frequency corresponding to the previous setting, nor the clock frequency corre-
sponding to the new setting.
The ripple counter that implements the prescaler runs at the frequency of the undivided clock,
which may be faster than the CPU's clock frequency. Hence, it is not possible to determine the
state of the prescaler - even if it were readable, and the exact time it takes to switch from one
clock division to the other cannot be exactly predicted. From the time the CLKPS values are writ-
ten, it takes between T1 + T2 and T1 + 2 * T2 before the new clock frequency is active. In this
interval, 2 active clock edges are produced. Here, T1 is the previous clock period, and T2 is the
period corresponding to the new prescaler setting.
To avoid unintentional changes of clock frequency, a special write procedure must be followed
to change the CLKPS bits:
1. Write the Clock Prescaler Change Enable (CLKPCE) bit to one and all other bits in
CLKPR to zero.
2. Within four cycles, write the desired value to CLKPS while writing a zero to CLKPCE.
Interrupts must be disabled when changing prescaler setting to make sure the write procedure is
not interrupted.
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8059D–AVR–11/09

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