ATMEGA644P-20PQ Atmel, ATMEGA644P-20PQ Datasheet - Page 155

• Manufacturer Part Number: ATMEGA644P-20PQ
• Description: MCU AVR 64K FLASH 20MHZ 40-PDIP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA644P-20PQ

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 32
• 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): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 40-DIP (0.600", 15.24mm)
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

14.11.2
8011O–AVR–07/10
TCCR2B – Timer/Counter Control Register B
• Bits 1:0 – WGM21:0: Waveform Generation Mode
Combined with the WGM22 bit found in the TCCR2B Register, these bits control the counting
sequence of the counter, the source for maximum (TOP) counter value, and what type of wave-
form generation to be used, see
unit are: Normal mode (counter), Clear Timer on Compare Match (CTC) mode, and two types of
Pulse Width Modulation (PWM) modes (see
Table 14-8.
Notes:
• Bit 7 – FOC2A: Force Output Compare A
The FOC2A bit is only active when the WGM bits specify a non-PWM mode.
However, for ensuring compatibility with future devices, this bit must be set to zero when
TCCR2B is written when operating in PWM mode. When writing a logical one to the FOC2A bit,
an immediate Compare Match is forced on the Waveform Generation unit. The OC2A output is
changed according to its COM2A1:0 bits setting. Note that the FOC2A bit is implemented as a
strobe. Therefore it is the value present in the COM2A1:0 bits that determines the effect of the
forced compare.
A FOC2A strobe will not generate any interrupt, nor will it clear the timer in CTC mode using
OCR2A as TOP.
The FOC2A bit is always read as zero.
Bit
(0xB1)
Read/Write
Initial Value
Mode
0
1
2
3
4
5
6
7
1. MAX= 0xFF
2. BOTTOM= 0x00
WGM2
0
0
0
0
1
1
1
1
Waveform Generation Mode Bit Description
FOC2A
W
7
0
WGM1
0
0
1
1
0
0
1
1
FOC2B
W
6
0
WGM0
Table
0
1
0
1
0
1
0
1
R
5
–
0
14-8. Modes of operation supported by the Timer/Counter
Timer/Counter
Mode of
Operation
Normal
PWM, Phase
Correct
CTC
Fast PWM
Reserved
PWM, Phase
Correct
Reserved
Fast PWM
”Modes of Operation” on page
R
4
–
0
ATmega164P/324P/644P
WGM22
R/W
3
0
OCRA
OCRA
OCRA
0xFF
0xFF
0xFF
TOP
CS22
–
–
R/W
2
0
Update of
Immediate
Immediate
BOTTOM
BOTTOM
OCRx at
CS21
R/W
1
0
TOP
TOP
–
–
144).
CS20
R/W
0
0
Set on
TOV Flag
BOTTOM
BOTTOM
MAX
MAX
MAX
TOP
TCCR2B
–
–
(1)(2)
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