ATmega8HVA Atmel Corporation, ATmega8HVA Datasheet - Page 27

• Manufacturer Part Number: ATmega8HVA
• Manufacturer: Atmel Corporation

Specifications of ATmega8HVA

• Flash (kbytes): 8 Kbytes
• Pin Count: 28
• Max. Operating Frequency: 4 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 3
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 6
• Ext Interrupts: 3
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 6
• Adc Resolution (bits): 12
• Adc Speed (ksps): 1.9
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 0.5
• Eeprom (bytes): 256
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -20 to 85
• I/o Supply Class: 1.8 to 9.0
• Operating Voltage (vcc): 1.8 to 9.0
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 4
• Input Capture Channels: 2
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

9.7
9.8
9.9
9.10
8024A–AVR–04/08
Watchdog Timer, Battery Protection and Coulomb Counter ADC Clock
Clock Startup Sequence
Clock Output
System Clock Prescaler
The clock source for the Watchdog Timer, Battery Protection and Coulomb Counter ADC (CC-
ADC) is the Ultra Low Power RC Oscillator. The Oscillator is automatically enabled in all opera-
tional modes. It is also enabled during reset.
When the CPU wakes up from Power-save, the CPU clock source is used to time the start-up,
ensuring a stable clock before instruction execution starts. When the CPU starts from reset,
there is an additional delay allowing the voltage regulator to reach a stable level before com-
mencing normal operation. The Ultra Low Power RC Oscillator is used for timing this real-time
part of the start-up time. Start-up times are determined by the SUT Fuses as shown in
on page
shown in
Table 9-2.
Note:
The CPU clock divided by 2 can be output to the PB0 pin. The CPU can enable the clock output
function by setting the CKOE bit in the MCU Control Register. The clock will not run in any sleep
modes.
The ATmega8HVA/16HVA has a System Clock Prescaler, used to prescale the Calibrated Fast
RC Oscillator. The system clock can be divided by setting the
ter” on page
as the requirement for power consumption and processing power changes. This system clock
will affect the clock frequency of the CPU and all synchronous peripherals. clk
FLASH
When switching between prescaler settings, the System Clock Prescaler ensures that no
glitches occurs in the clock system. It also ensures that no intermediate frequency is higher than
neither the clock frequency corresponding to the previous setting, nor the clock frequency corre-
sponding to the new setting.
are divided by a factor as shown in
1. The actual value depends on the actual clock period of the Ultra Low Power RC Oscillator,
25. The number of Ultra Low Power RC Oscillator cycles used for each time-out is
Table
refer to
31, and this enables the user to decrease or increase the system clock frequency
Number of Ultra Low Power RC Oscillator Cycles
9-2.
Typ Time-out
”Ultra Low Power RC Oscillator” on page 26
128 ms
256 ms
512 ms
16 ms
32 ms
64 ms
4 ms
8 ms
(1)
Table 9-3 on page
ATmega8HVA/16HVA
for details.
32.
”CLKPR – Clock Prescale Regis-
Number of Cycles
16K
32K
64K
512
1K
2K
4K
8K
I/O
, clk
CPU
Table 9-1
and clk-
27