ATMEGA6490A-AU Atmel, ATMEGA6490A-AU Datasheet - Page 98

• Manufacturer Part Number: ATMEGA6490A-AU
• Description: IC MCU AVR 64K FLASH 100TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA6490A-AU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, LCD, POR, PWM, WDT
• Number Of I /o: 69
• Program Memory Size: 64KB (32K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 2K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 100-TFQFP
• Processor Series: ATmega
• Core: AVR
• Data Bus Width: 8 bit
• Data Ram Size: 4 KB
• Interface Type: SPI, USART
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 69
• Number Of Timers: 3
• Operating Supply Voltage: 3.3 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Operating Temperature Range: - 40 C to + 85 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

14.2.2
14.3
14.4
8284A–AVR–10/10
Timer/Counter Clock Sources
Counter Unit
Definitions
The double buffered Output Compare Register (OCR0A) is compared with the Timer/Counter
value at all times. The result of the compare can be used by the Waveform Generator to gener-
ate a PWM or variable frequency output on the Output Compare pin (OC0A).
Compare Unit” on page 100.
Flag (OCF0A) which can be used to generate an Output Compare interrupt request.
Many register and bit references in this section are written in general form. A lower case “n”
replaces the Timer/Counter number, in this case 0. A lower case “x” replaces the Output Com-
pare unit number, in this case unit A. However, when using the register or bit defines in a
program, the precise form must be used, i.e., TCNT0 for accessing Timer/Counter0 counter
value and so on.
The definitions in
Table 14-1.
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 (CS02:0) bits
located in the Timer/Counter Control Register (TCCR0A). For details on clock sources and pres-
caler, see
The main part of the 8-bit Timer/Counter is the programmable bi-directional counter unit.
14-2
Figure 14-2. Counter Unit Block Diagram
Signal description (internal signals):
BOTTOM
MAX
TOP
ATmega169A/169PA/329A/329PA/649A/649P/3290A/3290PA/6490A/6490P
shows a block diagram of the counter and its surroundings.
count
direction
clear
”Timer/Counter Timing Diagrams” on page 107
Definitions of Timer/Counter values.
DATA BUS
The counter reaches the BOTTOM when it becomes 0x00.
The counter reaches its MAXimum when it becomes 0xFF (decimal 255).
The counter reaches the TOP when it becomes equal to the highest value in the
count sequence. The TOP value can be assigned to be the fixed value 0xFF
(MAX) or the value stored in the OCR0A Register. The assignment is depen-
dent on the mode of operation.
TCNTn
Table 14-1
are also used extensively throughout the document.
for details. The compare match event will also set the Compare
Increment or decrement TCNT0 by 1.
Select between increment and decrement.
Clear TCNT0 (set all bits to zero).
direction
count
clear
bottom
Control Logic
top
TOVn
(Int.Req.)
clk
Tn
and onwards.
Clock Select
( From Prescaler )
Detector
Edge
See ”Output
Tn
Figure
98