ATmega32 Atmel Corporation, ATmega32 Datasheet - Page 74
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ATmega32
Manufacturer Part Number
ATmega32
Description
Manufacturer
Atmel Corporation
Specifications of ATmega32
Flash (kbytes)
32 Kbytes
Pin Count
44
Max. Operating Frequency
16 MHz
Cpu
8-bit AVR
# Of Touch Channels
16
Hardware Qtouch Acquisition
No
Max I/o Pins
32
Ext Interrupts
3
Usb Speed
No
Usb Interface
No
Spi
1
Twi (i2c)
1
Uart
1
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)
2
Eeprom (bytes)
1024
Self Program Memory
YES
Dram Memory
No
Nand Interface
No
Picopower
No
Temp. Range (deg C)
-40 to 85
I/o Supply Class
2.7 to 5.5
Operating Voltage (vcc)
2.7 to 5.5
Fpu
No
Mpu / Mmu
no / no
Timers
3
Output Compare Channels
4
Input Capture Channels
1
Pwm Channels
4
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
ATmega32-16AC
Manufacturer:
COMPAL
Quantity:
500
Part Number:
ATmega32-16AU
Manufacturer:
ATMEL
Quantity:
20 000
Part Number:
ATmega32-16PI
Manufacturer:
ATMEL/爱特梅尔
Quantity:
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Part Number:
ATmega32-16PU
Manufacturer:
ATMEL/爱特梅尔
Quantity:
20 000
Clear Timer on
Compare Match (CTC)
Mode
2503Q–AVR–02/11
timer clock cycle as the TCNT0 becomes zero. The
bit, except that it is only set, not cleared. However, combined with the timer overflow interrupt
that automatically clears the
There are no special cases to consider in the normal mode, a new counter value can be written
anytime.
The output compare unit can be used to generate interrupts at some given time. Using the out-
put 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 (WGM01:0 = 2), the OCR0 Register is used to manip-
ulate the counter resolution. In CTC mode the counter is cleared to zero when the counter value
(TCNT0) matches the OCR0. The OCR0 defines the top value for the counter, hence also its
resolution. This mode allows greater control of the compare match output frequency. It also sim-
plifies the operation of counting external events.
The timing diagram for the CTC mode is shown in
increases until a compare match occurs between TCNT0 and OCR0, and then counter (TCNT0)
is cleared.
Figure 31. CTC Mode, Timing Diagram
An interrupt can be generated each time the counter value reaches the TOP value by using the
OCF0 Flag. If the interrupt is enabled, the interrupt handler routine can be used for updating the
TOP value. However, changing TOP to a value close to BOTTOM when the counter is running
with none or a low prescaler value must be done with care since the CTC mode does not have
the double buffering feature. If the new value written to OCR0 is lower than the current value of
TCNT0, the counter will miss the compare match. The counter will then have to count to its max-
imum value (0xFF) and wrap around starting at 0x00 before the compare match can occur.
For generating a waveform output in CTC mode, the OC0 output can be set to toggle its logical
level on each compare match by setting the Compare Output mode bits to toggle mode
(COM01:0 = 1). The OC0 value will not be visible on the port pin unless the data direction for the
pin is set to output. The waveform generated will have a maximum frequency of f
when OCR0 is set to zero (0x00). The waveform frequency is defined by the following equation:
The N variable represents the prescale factor (1, 8, 64, 256, or 1024).
As for the Normal mode of operation, the TOV0 Flag is set in the same timer clock cycle that the
counter counts from MAX to 0x00.
TCNTn
OCn
(Toggle)
Period
1
TOV
0 Flag, the timer resolution can be increased by software.
f
OCn
2
=
---------------------------------------------- -
2 N
⋅
⋅
f
(
clk_I/O
1
3
+
TOV
OCRn
Figure
0 Flag in this case behaves like a ninth
)
4
31. The counter value (TCNT0)
ATmega32(L)
OCn Interrupt Flag Set
(COMn1:0 = 1)
OC0
= f
clk_I/O
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