ATMEGA328P-20PU Atmel, ATMEGA328P-20PU Datasheet - Page 54
ATMEGA328P-20PU
Manufacturer Part Number
ATMEGA328P-20PU
Description
Manufacturer
Atmel
Datasheet
1.ATMEGA328P-20PU.pdf
(419 pages)
Specifications of ATMEGA328P-20PU
Cpu Family
ATmega
Device Core
AVR
Device Core Size
8b
Frequency (max)
20MHz
Interface Type
SPI/TWI/USART
Program Memory Type
Flash
Program Memory Size
32KB
Total Internal Ram Size
2KB
# I/os (max)
23
Number Of Timers - General Purpose
3
Operating Supply Voltage (typ)
3.3/5V
Operating Supply Voltage (max)
5.5V
Operating Supply Voltage (min)
2.7V
On-chip Adc
6-chx10-bit
Instruction Set Architecture
RISC
Operating Temp Range
-40C to 85C
Operating Temperature Classification
Industrial
Mounting
Through Hole
Pin Count
28
Package Type
PDIP
Lead Free Status / Rohs Status
Compliant
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10.9
10.9.1
10.9.2
8025K–AVR–10/09
Register Description
MCUSR – MCU Status Register
WDTCSR – Watchdog Timer Control Register
The MCU Status Register provides information on which reset source caused an MCU reset.
• Bit 7..4: Res: Reserved Bits
These bits are unused bits in the ATmega48P/88P/168P, and will always read as zero.
• Bit 3 – WDRF: Watchdog System Reset Flag
This bit is set if a Watchdog System Reset occurs. The bit is reset by a Power-on Reset, or by
writing a logic zero to the flag.
• Bit 2 – BORF: Brown-out Reset Flag
This bit is set if a Brown-out Reset occurs. The bit is reset by a Power-on Reset, or by writing a
logic zero to the flag.
• Bit 1 – EXTRF: External Reset Flag
This bit is set if an External Reset occurs. The bit is reset by a Power-on Reset, or by writing a
logic zero to the flag.
• Bit 0 – PORF: Power-on Reset Flag
This bit is set if a Power-on Reset occurs. The bit is reset only by writing a logic zero to the flag.
To make use of the Reset Flags to identify a reset condition, the user should read and then
Reset the MCUSR as early as possible in the program. If the register is cleared before another
reset occurs, the source of the reset can be found by examining the Reset Flags.
• Bit 7 - WDIF: Watchdog Interrupt Flag
This bit is set when a time-out occurs in the Watchdog Timer and the Watchdog Timer is config-
ured for interrupt. WDIF is cleared by hardware when executing the corresponding interrupt
handling vector. Alternatively, WDIF is cleared by writing a logic one to the flag. When the I-bit in
SREG and WDIE are set, the Watchdog Time-out Interrupt is executed.
• Bit 6 - WDIE: Watchdog Interrupt Enable
When this bit is written to one and the I-bit in the Status Register is set, the Watchdog Interrupt is
enabled. If WDE is cleared in combination with this setting, the Watchdog Timer is in Interrupt
Mode, and the corresponding interrupt is executed if time-out in the Watchdog Timer occurs. If
WDE is set, the Watchdog Timer is in Interrupt and System Reset Mode. The first time-out in the
Watchdog Timer will set WDIF. Executing the corresponding interrupt vector will clear WDIE and
Bit
0x35 (0x55)
Read/Write
Initial Value
Bit
(0x60)
Read/Write
Initial Value
WDIF
R/W
7
0
R
7
–
0
WDIE
R/W
6
0
R
6
–
0
WDP3
R/W
5
0
R
5
–
0
WDCE
R/W
4
0
R
4
–
0
WDE
WDRF
R/W
R/W
3
X
ATmega48P/88P/168P
3
WDP2
R/W
BORF
See Bit Description
R/W
2
0
2
WDP1
R/W
EXTRF
R/W
1
0
1
WDP0
R/W
PORF
0
0
R/W
0
WDTCSR
MCUSR
54
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