AT90USB647-MU Atmel, AT90USB647-MU Datasheet - Page 169

• 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

15.10.1
7593K–AVR–11/09
General Timer/Counter Control Register – GTCCR
The clock source for Timer/Counter2 is named clk
system I/O clock clk
clocked from the TOSC1 pin. This enables use of Timer/Counter2 as a Real Time Counter
(RTC). When AS2 is set, pins TOSC1 and TOSC2 are disconnected from Port C. A crystal can
then be connected between the TOSC1 and TOSC2 pins to serve as an independent clock
source for Timer/Counter2. The Oscillator is optimized for use with a 32.768 kHz crystal. Apply-
ing an external clock source to TOSC1 is not recommended.
For Timer/Counter2, the possible prescaled selections are: clk
clk
Setting the PSRASY bit in GTCCR resets the prescaler. This allows the user to operate with a
predictable prescaler.
• Bit 1 – PSRASY: Prescaler Reset Timer/Counter2
When this bit is one, the Timer/Counter2 prescaler will be reset. This bit is normally cleared
immediately by hardware. If the bit is written when Timer/Counter2 is operating in asynchronous
mode, the bit will remain one until the prescaler has been reset. The bit will not be cleared by
hardware if the TSM bit is set. Refer to the description of the
Register – GTCCR” on page 99
Bit
Read/Write
Initial Value
T2S
/128, clk
7
TSM
R/W
0
T2S
/256, and clk
6
–
R
0
IO
. By setting the AS2 bit in ASSR, Timer/Counter2 is asynchronously
5
–
R
0
T2S
for a description of the Timer/Counter Synchronization mode.
/1024. Additionally, clk
4
–
R
0
3
–
R
0
T2S
. clk
T2S
2
–
R
0
T2S
as well as 0 (stop) may be selected.
is by default connected to the main
“General Timer/Counter Control
1
PSRA-
SY
R/W
0
AT90USB64/128
T2S
/8, clk
0
PSRSY
NC
R/W
0
T2S
/32, clk
GTCCR
T2S
/64,
169