ATMEGA16HVA-4CKU Atmel, ATMEGA16HVA-4CKU Datasheet - Page 75

• Manufacturer Part Number: ATMEGA16HVA-4CKU
• Description: MCU AVR 16K FLASH 4MHZ 36-LGA
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA16HVA-4CKU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 4MHz
• Connectivity: SPI
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 7
• Program Memory Size: 16KB (8K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 9 V
• Data Converters: A/D 5x12b
• Oscillator Type: External
• Operating Temperature: -20°C ~ 85°C
• Package / Case: 36-LGA
• Processor Series: ATMEGA16x
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 512 B
• Interface Type: SPI
• Maximum Clock Frequency: 4 MHz
• Number Of Programmable I/os: 6
• Number Of Timers: 2
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: EWAVR, EWAVR-BL
• Development Tools By Supplier: ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT, ATAVRSB200, ATAVRSB201
• Minimum Operating Temperature: - 20 C
• On-chip Adc: 12 bit, 5 Channel
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32ATSTK500 - PROGRAMMER AVR STARTER KIT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

16.2
8024A–AVR–04/08
External Clock Source
An external clock source applied to the Tn pin can be used as Timer/Counter clock (clk
Tn pin is sampled once every system clock cycle by the pin synchronization logic. The synchro-
nized (sampled) signal is then passed through the edge detector.
equivalent block diagram of the Tn synchronization and edge detector logic. The registers are
clocked at the positive edge of the internal system clock (
high period of the internal system clock.
The edge detector generates one clk
= 6) edge it detects. See
Figure 16-2. Tn Pin Sampling
The synchronization and edge detector logic introduces a delay of 2.5 to 3.5 system clock cycles
from an edge has been applied to the Tn pin to the counter is updated.
Enabling and disabling of the clock input must be done when Tn has been stable for at least one
system clock cycle, otherwise it is a risk that a false Timer/Counter clock pulse is generated.
Each half period of the external clock applied must be longer than one system clock cycle to
ensure correct sampling. The external clock must be guaranteed to have less than half the sys-
tem clock frequency (f
sampling, the maximum frequency of an external clock it can detect is half the sampling fre-
quency (Nyquist sampling theorem). However, due to variation of the system clock frequency
and duty cycle caused by Oscillator source (crystal, resonator, and capacitors) tolerances, it is
recommended that maximum frequency of an external clock source is less than f
An external clock source can not be prescaled.
Tn
clk
I/O
D
LE
ExtClk
Q
Table 16-1 on page 76
Synchronization
< f
D
clk_I/O
Q
/2) given a 50/50% duty cycle. Since the edge detector uses
T
n
pulse for each positive (CSn2:0 = 7) or negative (CSn2:0
for details.
ATmega8HVA/16HVA
clk
D
I/O
). The latch is transparent in the
Q
Figure 16-2
Edge Detector
shows a functional
clk_I/O
Tn_sync
(To Clock
Select Logic)
/2.5.
Tn
). The
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