ATtiny40 Atmel Corporation, ATtiny40 Datasheet - Page 91

• Manufacturer Part Number: ATtiny40
• Manufacturer: Atmel Corporation

Specifications of ATtiny40

• Flash (kbytes): 4 Kbytes
• Pin Count: 20
• Max. Operating Frequency: 12 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 12
• Hardware Qtouch Acquisition: Yes
• Max I/o Pins: 18
• Ext Interrupts: 18
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 12
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 0.25
• Self Program Memory: NO
• 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: 2
• Output Compare Channels: 4
• Input Capture Channels: 1
• Pwm Channels: 2
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

8263A–AVR–08/10
access. The same temporary register is shared between all 16-bit registers. Accessing the low
byte triggers the 16-bit read or write operation. When the low byte of a 16-bit register is written
by the CPU, the high byte stored in the temporary register, and the low byte written are both cop-
ied into the 16-bit register in the same clock cycle. When the low byte of a 16-bit register is read
by the CPU, the high byte of the 16-bit register is copied into the temporary register in the same
clock cycle as the low byte is read.
There is one exception in the temporary register usage. In the Output Compare mode the 16-bit
Output Compare Register OCR1A/B is read without the temporary register, because the Output
Compare Register contains a fixed value that is only changed by CPU access. However, in 16-
bit Input Capture mode the ICR1 register formed by the OCR1A and OCR1B registers must be
accessed with the temporary register.
To do a 16-bit write, the high byte must be written before the low byte. For a 16-bit read, the low
byte must be read before the high byte.
The following code examples show how to access the 16-bit timer registers assuming that no
interrupts updates the temporary register. The same principle can be used directly for accessing
the OCR1A/B registers.
Note:
The assembly code example returns the TCNT1H/L value in the r17:r16 register pair.
It is important to notice that accessing 16-bit registers are atomic operations. If an interrupt
occurs between the two instructions accessing the 16-bit register, and the interrupt code
updates the temporary register by accessing the same or any other of the 16-bit timer registers,
Assembly Code Example
C Code Example
unsigned int i;
...
/* Set TCNT1 to 0x01FF */
TCNT1H = 0x01;
TCNT1L = 0xff;
/* Read TCNT1 into i */
i = TCNT1L;
i |= ((unsigned int)TCNT1H << 8);
...
...
; Set TCNT
ldi r17,0x01
ldi r16,0xFF
out TCNT1H,r17
out TCNT1L,r16
; Read TCNT1 into r17:r16
in r16,TCNT1L
in r17,TCNT1H
...
See
“Code Examples” on page
1
to 0x01FF
6.
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