ATmega6490 Atmel Corporation, ATmega6490 Datasheet - Page 116
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ATmega6490
Manufacturer Part Number
ATmega6490
Description
Manufacturer
Atmel Corporation
Specifications of ATmega6490
Flash (kbytes)
64 Kbytes
Pin Count
100
Max. Operating Frequency
16 MHz
Cpu
8-bit AVR
# Of Touch Channels
16
Hardware Qtouch Acquisition
No
Max I/o Pins
69
Ext Interrupts
32
Usb Speed
No
Usb Interface
No
Spi
2
Twi (i2c)
1
Uart
1
Segment Lcd
160
Graphic Lcd
No
Video Decoder
No
Camera Interface
No
Adc Channels
8
Adc Resolution (bits)
10
Adc Speed (ksps)
15
Analog Comparators
1
Resistive Touch Screen
No
Temp. Sensor
No
Crypto Engine
No
Sram (kbytes)
4
Eeprom (bytes)
2048
Self Program Memory
YES
Dram Memory
No
Nand Interface
No
Picopower
No
Temp. Range (deg C)
-40 to 85
I/o Supply Class
1.8 to 5.5
Operating Voltage (vcc)
1.8 to 5.5
Fpu
No
Mpu / Mmu
no / no
Timers
3
Output Compare Channels
4
Input Capture Channels
1
Pwm Channels
4
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes
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Price
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779
16.4
16.5
116
Timer/Counter Clock Sources
Counter Unit
ATmega329/3290/649/6490
The Timer/Counter can be clocked by an internal or an external clock source. The clock source
is selected by the Clock Select logic which is controlled by the Clock Select (CS12:0) bits
located in the Timer/Counter control Register B (TCCR1B). For details on clock sources and
prescaler, see
The main part of the 16-bit Timer/Counter is the programmable 16-bit bi-directional counter unit.
Figure 16-2
Figure 16-2. Counter Unit Block Diagram
Signal description (internal signals):
The 16-bit counter is mapped into two 8-bit I/O memory locations: Counter High (TCNT1H) con-
taining the upper eight bits of the counter, and Counter Low (TCNT1L) containing the lower eight
bits. The TCNT1H Register can only be indirectly accessed by the CPU. When the CPU does an
access to the TCNT1H I/O location, the CPU accesses the high byte temporary register (TEMP).
The temporary register is updated with the TCNT1H value when the TCNT1L is read, and
TCNT1H is updated with the temporary register value when TCNT1L is written. This allows the
CPU to read or write the entire 16-bit counter value within one clock cycle via the 8-bit data bus.
It is important to notice that there are special cases of writing to the TCNT1 Register when the
counter is counting that will give unpredictable results. The special cases are described in the
sections where they are of importance.
Depending on the mode of operation used, the counter is cleared, incremented, or decremented
at each timer clock (clk
selected by the Clock Select bits (CS12:0). When no clock source is selected (CS12:0 = 0) the
timer is stopped. However, the TCNT1 value can be accessed by the CPU, independent of
Count
Direction
Clear
clk
TOP
BOTTOM
T
1
TCNTnH (8-bit)
TEMP (8-bit)
shows a block diagram of the counter and its surroundings.
“Timer/Counter0 and Timer/Counter1 Prescalers” on page
TCNTn (16-bit Counter)
DATA BUS
T
1
). The clk
TCNTnL (8-bit)
(8-bit)
Increment or decrement TCNT1 by 1.
Select between increment and decrement.
Clear TCNT1 (set all bits to zero).
Timer/Counter clock.
Signalize that TCNT1 has reached maximum value.
Signalize that TCNT1 has reached minimum value (zero).
T
1
can be generated from an external or internal clock source,
Direction
Count
Clear
Control Logic
TOP
BOTTOM
TOVn
(Int.Req.)
clk
Tn
Clock Select
( From Prescaler )
Detector
Edge
107.
2552K–AVR–04/11
Tn