ATtiny87 Atmel Corporation, ATtiny87 Datasheet - Page 57
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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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6.3.3
8265B–AVR–09/10
WDTCR – Watchdog Timer Control Register
• Bit 7 – WDIF: Watchdog Interrupt Flag
This bit is set when a time-out occurs in the Watchdog Timer and the Watchdog Timer is con-
figured 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 Inter-
rupt 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 WDIF automatically by hardware (the Watchdog goes to System Reset Mode). This
is useful for keeping the Watchdog Timer security while using the interrupt. To stay in Interrupt
and System Reset Mode, WDIE must be set after each interrupt. This should however not be
done within the interrupt service routine itself, as this might compromise the safety-function of
the Watchdog System Reset mode. If the interrupt is not executed before the next time-out, a
System Reset will be applied.
If the Watchdog Timer is used as clock monitor (c.f.
Control Bits 3 - 0” on page
automatically disabled.
Table 6-1.
Note:
• Bit 4 – WDCE: Watchdog Change Enable
This bit is used in timed sequences for changing WDE and prescaler bits. To clear the WDE
bit, and/or change the prescaler bits, WDCE must be set.
Once written to one, hardware will clear WDCE after four clock cycles.
Bit
(0x60)
Read/Write
Initial Value
Monitor
Clock
On
Off
x
1. At least one of these three enables (WDTON, WDE & WDIE) equal to 1.
WDTON
Watchdog Timer Configuration
WDIF
R/W
y
0
0
0
0
1
7
0
(1)
WDE
WDIE
R/W
y
0
0
1
1
x
6
0
(1)
40), the System Reset Mode is enabled and the Interrupt Mode is
WDIE Mode
WDP3
y
0
1
0
1
x
R/W
(1)
5
0
Stopped
System Reset Mode
Interrupt Mode
System Reset Mode
Interrupt and System Reset
Mode
System Reset Mode
WDCE
R/W
4
0
WDE
R/W
3
X
Section • “Bits 3:0 – CLKC[3:0]: Clock
WDP2
R/W
2
0
Action on Time-out
None
Reset
Interrupt
Reset
Interrupt, then go to System
Reset Mode
Reset
WDP1
R/W
1
0
WDP0
R/W
0
0
WDTCR
57