ATtiny87 Atmel Corporation, ATtiny87 Datasheet - Page 112
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ATtiny87
Manufacturer Part Number
ATtiny87
Description
Manufacturer
Atmel Corporation
Specifications of ATtiny87
Flash (kbytes)
8 Kbytes
Pin Count
20
Max. Operating Frequency
16 MHz
Cpu
8-bit AVR
Hardware Qtouch Acquisition
No
Max I/o Pins
16
Ext Interrupts
16
Usb Speed
No
Usb Interface
No
Spi
2
Twi (i2c)
1
Uart
1
Lin
1
Graphic Lcd
No
Video Decoder
No
Camera Interface
No
Adc Channels
11
Adc Resolution (bits)
10
Adc Speed (ksps)
15
Analog Comparators
1
Resistive Touch Screen
No
Temp. Sensor
Yes
Crypto Engine
No
Sram (kbytes)
0.5
Eeprom (bytes)
512
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
2
Output Compare Channels
3
Input Capture Channels
1
Pwm Channels
9
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes
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12.2.2
12.3
112
Accessing 16-bit Registers
ATtiny87/ATtiny167
Definitions
The Timer/Counter can be clocked internally, via the prescaler, or by an external clock source
on the Tn pin. The Clock Select logic block controls which clock source and edge the
Timer/Counter uses to increment (or decrement) its value. The Timer/Counter is inactive when
no clock source is selected. The output from the Clock Select logic is referred to as the timer
clock (clk
The double buffered Output Compare Registers (OCR1A/B) are compared with the
Timer/Counter value at all time. The result of the compare can be used by the Waveform Gen-
erator to generate a PWM or variable frequency output on the Output Compare pins
”Output Compare Units” on page
Match Flag (OCF1A/B) which can be used to generate an Output Compare interrupt request.
The Input Capture Register can capture the Timer/Counter value at a given external (edge
triggered) event on either the Input Capture pin (ICP1) or on the Analog Comparator pins
”AnaComp - Analog Comparator” on page
ing unit (Noise Canceler) for reducing the chance of capturing noise spikes.
The TOP value, or maximum Timer/Counter value, can in some modes of operation be
defined by either the OCR1A Register, the ICR1 Register, or by a set of fixed values. When
using OCR1A as TOP value in a PWM mode, the OCR1A Register can not be used for gener-
ating a PWM output. However, the TOP value will in this case be double buffered allowing the
TOP value to be changed in run time. If a fixed TOP value is required, the ICR1 Register can
be used as an alternative, freeing the OCR1A to be used as PWM output.
The following definitions are used extensively throughout the section:
The TCNT1, OCR1A/B, and ICR1 are 16-bit registers that can be accessed by the AVR CPU
via the 8-bit data bus. The 16-bit register must be byte accessed using two read or write oper-
ations. Each 16-bit timer has a single 8-bit register for temporary storing of the high byte of the
16-bit access. The same temporary register is shared between all 16-bit registers within each
16-bit timer. 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 copied 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 cop-
ied into the temporary register in the same clock cycle as the low byte is read.
Not all 16-bit accesses uses the temporary register for the high byte. Reading the OCR1A/B
16-bit registers does not involve using 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.
BOTTOM
MAX
TOP
T
n
).
The counter reaches the BOTTOM when it becomes 0x0000.
The counter reaches its MAXimum when it becomes 0xFFFF (decimal 65,535).
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 one of the fixed val-
ues: 0x00FF, 0x01FF, or 0x03FF, or to the value stored in the OCR1A or ICR1
Register. The assignment is dependent of the mode of operation.
119.. The compare match event will also set the Compare
211.). The Input Capture unit includes a digital filter-
8265B–AVR–09/10
(See
See