ATmega1284 Atmel Corporation, ATmega1284 Datasheet - Page 136

• Manufacturer Part Number: ATmega1284
• Manufacturer: Atmel Corporation

Specifications of ATmega1284

• Flash (kbytes): 128 Kbytes
• Pin Count: 44
• Max. Operating Frequency: 20 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 32
• Ext Interrupts: 32
• Usb Speed: No
• Usb Interface: No
• Spi: 3
• Twi (i2c): 1
• Uart: 2
• 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): 16
• Eeprom (bytes): 4096
• 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: 6
• Input Capture Channels: 1
• Pwm Channels: 6
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

16.11.4
16.11.5
16.11.6
8272C–AVR–06/11
TCNT1H and TCNT1L –Timer/Counter1
TCNT3H and TCNT3L –Timer/Counter3
OCR1AH and OCR1AL – Output Compare Register1 A
A FOCnA/FOCnB strobe will not generate any interrupt nor will it clear the timer in Clear Timer
on Compare match (CTC) mode using OCRnA as TOP.
The FOCnA/FOCnB bits are always read as zero.
The two Timer/Counter I/O locations (TCNT1H and TCNT1L, combined TCNT1) give direct
access, both for read and for write operations, to the Timer/Counter unit 16-bit counter. To
ensure that both the high and low bytes are read and written simultaneously when the CPU
accesses these registers, the access is performed using an 8-bit temporary High Byte Register
(TEMP). This temporary register is shared by all the other 16-bit registers. See “Accessing 16-bit
Registers” on page 113.
Modifying the counter (TCNT1) while the counter is running introduces a risk of missing a com-
pare match between TCNT1 and one of the OCRnx Registers.
Writing to the TCNT1 Register blocks (removes) the compare match on the following timer clock
for all compare units.
The two Timer/Counter I/O locations (TCNT3H and TCNT3L, combined TCNT3) give direct
access, both for read and for write operations, to the Timer/Counter unit 16-bit counter. To
ensure that both the high and low bytes are read and written simultaneously when the CPU
accesses these registers, the access is performed using an 8-bit temporary High Byte Register
(TEMP). This temporary register is shared by all the other 16-bit registers. See “Accessing 16-bit
Registers” on page 113.
Modifying the counter (TCNT3) while the counter is running introduces a risk of missing a com-
pare match between TCNT3 and one of the OCRnx Registers.
Writing to the TCNT3 Register blocks (removes) the compare match on the following timer clock
for all compare units.
Bit
(0x85)
(0x84)
Read/Write
Initial Value
Bit
(0x95)
(0x94)
Read/Write
Initial Value
Bit
(0x89)
(0x88)
Read/Write
Initial Value
ATmega164A/PA/324A/PA/644A/PA/1284/P
R/W
R/W
R/W
7
0
7
0
7
0
R/W
R/W
R/W
6
0
6
0
6
0
R/W
R/W
R/W
5
0
5
0
5
0
R/W
R/W
R/W
4
0
4
0
4
OCR1A[15:8]
0
TCNT1[15:8]
TCNT3[15:8]
OCR1A[7:0]
TCNT1[7:0]
TCNT3[7:0]
R/W
R/W
R/W
3
0
3
0
3
0
R/W
R/W
R/W
2
0
2
0
2
0
R/W
R/W
R/W
1
0
1
0
1
0
R/W
R/W
R/W
0
0
0
0
0
0
OCR1AH
OCR1AL
TCNT1H
TCNT3H
TCNT1L
TCNT3L
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