ATMEGA128-16MN Atmel, ATMEGA128-16MN Datasheet - Page 174

• Manufacturer Part Number: ATMEGA128-16MN
• Description: MCU AVR 128KB FLASH 16MHZ 64QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA128-16MN

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: EBI/EMI, I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 128KB (64K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 4K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-MLF®, 64-QFN
• Processor Series: ATMEGA128x
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 4 KB
• 3rd Party Development Tools: EWAVR, EWAVR-BL
• Development Tools By Supplier: ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32ATSTK501 - ADAPTER KIT FOR 64PIN AVR MCUATSTK500 - PROGRAMMER AVR STARTER KIT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

External Clock
Synchronous Clock
Operation
174
ATmega128
External clocking is used by the synchronous slave modes of operation. The description in this
section refers to
External clock input from the XCK pin is sampled by a synchronization register to minimize the
chance of meta-stability. The output from the synchronization register must then pass through
an edge detector before it can be used by the transmitter and receiver. This process introduces
a two CPU clock period delay and therefore the maximum external XCK clock frequency is lim-
ited by the following equation:
Note that f
add some margin to avoid possible loss of data due to frequency variations.
When Synchronous mode is used (UMSEL = 1), the XCK pin will be used as either clock input
(slave) or clock output (master). The dependency between the clock edges and data sampling or
data change is the same. The basic principle is that data input (on RxD) is sampled at the oppo-
site XCK clock edge of the edge the data output (TxD) is changed.
Figure 81. Synchronous Mode XCK Timing.
The UCPOL bit UCRSC selects which XCK clock edge is used for data sampling and which is
used for data change. As
ing XCK edge and sampled at falling XCK edge. If UCPOL is set, the data will be changed at
falling XCK edge and sampled at rising XCK edge.
UCPOL = 1
UCPOL = 0
osc
depends on the stability of the system clock source. It is therefore recommended to
Figure 80
RxD / TxD
RxD / TxD
XCK
XCK
Figure 81
for details.
shows, when UCPOL is zero the data will be changed at ris-
f
XCK
<
f
---------- -
OSC
4
Sample
Sample
2467V–AVR–02/11