ATTINY861-20SU Atmel, ATTINY861-20SU Datasheet - Page 47

• Manufacturer Part Number: ATTINY861-20SU
• Description: IC MCU AVR 8K FLASH 20MHZ 20SOIC
• Manufacturer: Atmel
• Series: AVR® ATtinyr

Specifications of ATTINY861-20SU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: USI
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 16
• Program Memory Size: 8KB (4K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 11x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 20-SOIC (7.5mm Width)
• Cpu Family: ATtiny
• Device Core: AVR
• Device Core Size: 8b
• Frequency (max): 20MHz
• Interface Type: USI
• Total Internal Ram Size: 512Byte
• # I/os (max): 16
• Number Of Timers - General Purpose: 2
• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 2.7V
• On-chip Adc: 11-chx10-bit
• Instruction Set Architecture: RISC
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 20
• Package Type: SOIC
• Processor Series: ATTINY8x
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 512 B
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 16
• Number Of Timers: 2
• Operating Supply Voltage: 2.7 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: EWAVR, EWAVR-BL
• Development Tools By Supplier: ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT, ATAVRMC320
• Minimum Operating Temperature: - 40 C
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32ATAVRBC100 - REF DESIGN KIT BATTERY CHARGER770-1007 - ISP 4PORT ATMEL AVR MCU SPI/JTAG770-1004 - ISP 4PORT FOR ATMEL AVR MCU SPI
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8.4
8.4.1
8.4.2
2588E–AVR–08/10
Register Description
MCUSR – MCU Status Register
WDTCR – Watchdog Timer Control Register
The MCU Status Register provides information on which reset source caused an MCU Reset.
• Bits 7:4 – Res: Reserved Bits
These bits are reserved bits in the ATtiny261/461/861 and will always read as zero.
• Bit 3 – WDRF: Watchdog Reset Flag
This bit is set if a Watchdog 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 Timeout 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 Timeout Interrupt Enable
When this bit is written to one, WDE is cleared, and the I-bit in the Status Register is set, the
Watchdog Time-out Interrupt is enabled. In this mode the corresponding interrupt is executed
instead of a reset if a timeout in the Watchdog Timer occurs.
If WDE is set, WDIE is automatically cleared by hardware when a time-out occurs. This is useful
for keeping the Watchdog Reset security while using the interrupt. After the WDIE bit is cleared,
Bit
0x34 (0x54)
Read/Write
Initial Value
Bit
0x21 (0x41)
Read/Write
Initial Value
7
WDIF
R/W
0
7
–
R
0
6
WDIE
R/W
0
6
–
R
0
5
WDP3
R/W
0
5
–
R
0
4
WDCE
R/W
0
4
–
R
0
3
WDE
R/W
X
3
WDRF
R/W
See Bit Description
2
WDP2
R/W
0
2
BORF
R/W
1
WDP1
R/W
0
1
EXTRF
R/W
0
WDP0
R/W
0
0
PORF
R/W
WDTCR
MCUSR
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