ATtiny87 Atmel Corporation, ATtiny87 Datasheet - Page 123
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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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12.9.1
12.9.2
8265B–AVR–09/10
Normal Mode
Clear Timer on Compare Match (CTC) Mode
or toggle at a compare match
bits over control the setting of the COM1A/B[1:0] bits as shown in
For detailed timing information refer to
The simplest mode of operation is the Normal mode (WGM1[3:0] = 0). In this mode the count-
ing direction is always up (incrementing), and no counter clear is performed. The counter
simply overruns when it passes its maximum 16-bit value (MAX = 0xFFFF) and then restarts
from the BOTTOM (0x0000). In normal operation the Timer/Counter Overflow Flag (TOV1) will
be set in the same timer clock cycle as the TCNT1 becomes zero. The TOV1 flag in this case
behaves like a 17th bit, except that it is only set, not cleared. However, combined with the
timer overflow interrupt that automatically clears the TOV1 flag, the timer resolution can be
increased by software. There are no special cases to consider in the Normal mode, a new
counter value can be written anytime.
The Input Capture unit is easy to use in Normal mode. However, observe that the maximum
interval between the external events must not exceed the resolution of the counter. If the inter-
val between events are too long, the timer overflow interrupt or the prescaler must be used to
extend the resolution for the capture unit.
The Output Compare units can be used to generate interrupts at some given time. Using the
Output Compare to generate waveforms in Normal mode is not recommended, since this will
occupy too much of the CPU time.
In Clear Timer on Compare or CTC mode (WGM1[3:0] = 4 or 12), the OCR1A or ICR1 Regis-
ter are used to manipulate the counter resolution. In CTC mode the counter is cleared to zero
when the counter value (TCNT1) matches either the OCR1A (WGM1[3:0] = 4) or the ICR1
(WGM1[3:0] = 12). The OCR1A or ICR1 define the top value for the counter, hence also its
resolution. This mode allows greater control of the compare match output frequency. It also
simplifies the operation of counting external events.
The timing diagram for the CTC mode is shown in
increases until a compare match occurs with either OCR1A or ICR1, and then counter
(TCNT1) is cleared.
Figure 12-7. CTC Mode, Timing Diagram
TCNTn
OCnAi
(Toggle)
Period
1
(See ”Compare Match Output Unit” on page
2
“Timer/Counter Timing Diagrams” on page
3
4
Figure
12-7. The counter value (TCNT1)
Figure 12-6 on page
OCnA Interrupt Flag Set
or ICFn Interrupt Flag Set
(Interrupt on TOP)
(COMnA1:0 = 1)
120.). The OCnxi
130.
122.
123