ATMEGA164P-20AQ Atmel, ATMEGA164P-20AQ Datasheet - Page 157

• Manufacturer Part Number: ATMEGA164P-20AQ
• Description: MCU AVR 16K FLASH 20MHZ 44-TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA164P-20AQ

• 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: 16KB (8K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 1K 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: 44-TQFP, 44-VQFP
• For Use With: ATSTK600-TQFP44 - STK600 SOCKET/ADAPTER 44-TQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

14.11.4
14.11.5
14.11.6
8011O–AVR–07/10
OCR2A – Output Compare Register A
OCR2B – Output Compare Register B
ASSR – Asynchronous Status Register
Match on the following timer clock. Modifying the counter (TCNT2) while the counter is running,
introduces a risk of missing a Compare Match between TCNT2 and the OCR2x Registers.
The Output Compare Register A contains an 8-bit value that is continuously compared with the
counter value (TCNT2). A match can be used to generate an Output Compare interrupt, or to
generate a waveform output on the OC2A pin.
The Output Compare Register B contains an 8-bit value that is continuously compared with the
counter value (TCNT2). A match can be used to generate an Output Compare interrupt, or to
generate a waveform output on the OC2B pin.
• Bit 6 – EXCLK: Enable External Clock Input
When EXCLK is written to one, and asynchronous clock is selected, the external clock input buf-
fer is enabled and an external clock can be input on Timer Oscillator 1 (TOSC1) pin instead of a
32 kHz crystal. Writing to EXCLK should be done before asynchronous operation is selected.
Note that the crystal Oscillator will only run when this bit is zero.
• Bit 5 – AS2: Asynchronous Timer/Counter2
When AS2 is written to zero, Timer/Counter2 is clocked from the I/O clock, clk
written to one, Timer/Counter2 is clocked from a crystal Oscillator connected to the Timer Oscil-
lator 1 (TOSC1) pin. When the value of AS2 is changed, the contents of TCNT2, OCR2A,
OCR2B, TCCR2A and TCCR2B might be corrupted.
• Bit 4 – TCN2UB: Timer/Counter2 Update Busy
When Timer/Counter2 operates asynchronously and TCNT2 is written, this bit becomes set.
When TCNT2 has been updated from the temporary storage register, this bit is cleared by hard-
ware. A logical zero in this bit indicates that TCNT2 is ready to be updated with a new value.
• Bit 3 – OCR2AUB: Output Compare Register2 Update Busy
When Timer/Counter2 operates asynchronously and OCR2A is written, this bit becomes set.
When OCR2A has been updated from the temporary storage register, this bit is cleared by hard-
ware. A logical zero in this bit indicates that OCR2A is ready to be updated with a new value.
Bit
(0xB3)
Read/Write
Initial Value
Bit
(0xB4)
Read/Write
Initial Value
Bit
(0xB6)
Read/Write
Initial Value
R
7
–
0
R/W
R/W
7
0
7
0
EXCLK
R/W
6
0
R/W
R/W
6
0
6
0
R/W
AS2
5
0
R/W
R/W
TCN2UB
5
0
5
0
R
4
0
R/W
R/W
4
0
4
0
OCR2AUB
OCR2A[7:0]
OCR2B[7:0]
R
3
0
ATmega164P/324P/644P
R/W
R/W
3
0
3
0
OCR2BUB
R
2
0
R/W
R/W
2
0
2
0
TCR2AUB
R/W
R/W
R
1
0
1
0
1
0
TCR2BUB
I/O
R/W
R/W
0
0
0
0
. When AS2 is
R
0
0
OCR2A
OCR2B
ASSR
157