AT90USB647-MU Atmel, AT90USB647-MU Datasheet - Page 65
AT90USB647-MU
Manufacturer Part Number
AT90USB647-MU
Description
MCU, 8BIT, 64K FLASH, USB, 64QFN
Manufacturer
Atmel
Specifications of AT90USB647-MU
Controller Family/series
AT90
No. Of I/o's
48
Eeprom Memory Size
2KB
Ram Memory Size
4KB
Cpu Speed
16MHz
No. Of
RoHS Compliant
Core Size
8bit
Program Memory Size
64KB
Oscillator Type
External, Internal
Package
64QFN EP
Device Core
AVR
Family Name
AT90
Maximum Speed
20 MHz
Ram Size
4 KB
Operating Supply Voltage
3.3|5 V
Data Bus Width
8 Bit
Program Memory Type
Flash
Number Of Programmable I/os
48
Interface Type
SPI/TWI/USART/USB
On-chip Adc
8-chx10-bit
Operating Temperature
-40 to 85 °C
Number Of Timers
4
Lead Free Status / Rohs Status
Details
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8.8.1
7593K–AVR–11/09
Watchdog Timer Control Register - WDTCSR
Note: If the Watchdog is accidentally enabled, for example by a runaway pointer or brown-out
condition, the device will be reset and the Watchdog Timer will stay enabled. If the code is not
set up to handle the Watchdog, this might lead to an eternal loop of time-out resets. To avoid this
situation, the application software should always clear the Watchdog System Reset Flag
(WDRF) and the WDE control bit in the initialisation routine, even if the Watchdog is not in use.
The following code example shows one assembly and one C function for changing the time-out
value of the Watchdog Timer.
Note:
Note: The Watchdog Timer should be reset before any change of the WDP bits, since a change
in the WDP bits can result in a time-out when switching to a shorter time-out period.
Bit
Read/Write
Initial Value
Assembly Code Example
C Code Example
WDT_Prescaler_Change:
void WDT_Prescaler_Change(void)
{
}
; Turn off global interrupt
cli
; Reset Watchdog Timer
wdr
; Start timed sequence
in
ori
out
; --
; Set new prescaler(time-out) value = 64K cycles (~0.5 s)
ldi
out
; --
; Turn on global interrupt
sei
ret
__disable_interrupt();
__watchdog_reset();
/* Start timed
WDTCSR |= (1<<WDCE) | (1<<WDE);
/* Set new prescaler(time-out) value = 64K cycles (~0.5 s) */
WDTCSR
__enable_interrupt();
1. The example code assumes that the part specific header file is included.
7
WDIF
R/W
0
r16, WDTCSR
r16, (1<<WDCE) | (1<<WDE)
WDTCSR, r16
Got four cycles to set the new values from here -
r16, (1<<WDE) | (1<<WDP2) | (1<<WDP0)
WDTCSR, r16
Finished setting new values, used 2 cycles -
= (1<<WDE) | (1<<WDP2) | (1<<WDP0);
(1)
6
WDIE
R/W
0
(1)
equence */
5
WDP3
R/W
0
4
WDCE
R/W
0
3
WDE
X
R/W
2
WDP2
R/W
0
1
WDP1
R/W
0
AT90USB64/128
0
WDP0
R/W
0
WDTCSR
65
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