ATMEGA48A-PU Atmel, ATMEGA48A-PU Datasheet - Page 127

IC MCU AVR 4K FLASH 28PDIP

ATMEGA48A-PU

Manufacturer Part Number
ATMEGA48A-PU
Description
IC MCU AVR 4K FLASH 28PDIP
Manufacturer
Atmel
Series
AVR® ATmegar
Datasheets

Specifications of ATMEGA48A-PU

Core Processor
AVR
Core Size
8-Bit
Speed
20MHz
Connectivity
I²C, SPI, UART/USART
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
23
Program Memory Size
4KB (2K x 16)
Program Memory Type
FLASH
Eeprom Size
256 x 8
Ram Size
512 x 8
Voltage - Supply (vcc/vdd)
1.8 V ~ 5.5 V
Data Converters
A/D 6x10b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
28-DIP (0.300", 7.62mm)
Controller Family/series
Atmega
No. Of I/o's
23
Eeprom Memory Size
256Byte
Ram Memory Size
512Byte
Cpu Speed
20MHz
Rohs Compliant
Yes
Lead Free Status / RoHS Status
Lead free / RoHS Compliant

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Part Number:
ATMEGA48A-PU
Manufacturer:
Microchip Technology
Quantity:
1 051
15.9.3
8271C–AVR–08/10
Fast PWM Mode
Figure 15-6. CTC Mode, Timing Diagram
An interrupt can be generated at each time the counter value reaches the TOP value by either
using the OCF1A or ICF1 Flag according to the register used to define the TOP value. If the
interrupt is enabled, the interrupt handler routine can be used for updating the TOP value. How-
ever, changing the 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 buff-
ering feature. If the new value written to OCR1A or ICR1 is lower than the current value of
TCNT1, the counter will miss the compare match. The counter will then have to count to its max-
imum value (0xFFFF) and wrap around starting at 0x0000 before the compare match can occur.
In many cases this feature is not desirable. An alternative will then be to use the fast PWM mode
using OCR1A for defining TOP (WGM13:0 = 15) since the OCR1A then will be double buffered.
For generating a waveform output in CTC mode, the OC1A output can be set to toggle its logical
level on each compare match by setting the Compare Output mode bits to toggle mode
(COM1A1:0 = 1). The OC1A value will not be visible on the port pin unless the data direction for
the pin is set to output (DDR_OC1A = 1). The waveform generated will have a maximum fre-
quency of f
defined by the following equation:
The N variable represents the prescaler factor (1, 8, 64, 256, or 1024).
As for the Normal mode of operation, the TOV1 Flag is set in the same timer clock cycle that the
counter counts from MAX to 0x0000.
The fast Pulse Width Modulation or fast PWM mode (WGM13:0 = 5, 6, 7, 14, or 15) provides a
high frequency PWM waveform generation option. The fast PWM differs from the other PWM
options by its single-slope operation. The counter counts from BOTTOM to TOP then restarts
from BOTTOM. In non-inverting Compare Output mode, the Output Compare (OC1x) is cleared
on the compare match between TCNT1 and OCR1x, and set at BOTTOM. In inverting Compare
Output mode output is set on compare match and cleared at BOTTOM. Due to the single-slope
operation, the operating frequency of the fast PWM mode can be twice as high as the phase cor-
rect and phase and frequency correct PWM modes that use dual-slope operation. This high
frequency makes the fast PWM mode well suited for power regulation, rectification, and DAC
applications. High frequency allows physically small sized external components (coils, capaci-
tors), hence reduces total system cost.
ATmega48A/48PA/88A/88PA/168A/168PA/328/328
TCNTn
OCnA
(Toggle)
Period
OC
1
A
= f
clk_I/O
1
/2 when OCR1A is set to zero (0x0000). The waveform frequency is
f
OCnA
2
=
-------------------------------------------------- -
2 N
3
(
f
1
clk_I/O
+
4
OCRnA
)
OCnA Interrupt Flag Set
or ICFn Interrupt Flag Set
(Interrupt on TOP)
(COMnA1:0 = 1)
127

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