AT90CAN128-16AE ATMEL Corporation, AT90CAN128-16AE Datasheet - Page 159

• Manufacturer Part Number: AT90CAN128-16AE
• Description: 8-bit Avr Microcontroller With 128K Bytes of Isp Flash And CAN Controller.flash (Kbytes) 128 Vcc (V) 2.7-5.5 EEPROM (Kbytes) 4 SRAM (bytes) 4K CAN (mess. Obj.) 15
• Manufacturer: ATMEL Corporation

Timer/Counter2
Prescaler
General Timer/Counter
Control Register – GTCCR
4250C–CAN–03/04
Figure 72. Prescaler for Timer/Counter2
The clock source for Timer/Counter2 is named clk
the main system I/O clock clk
chronously clocked from the TOSC oscillator or TOSC1 pin. This enables use of
Timer/Counter2 as a Real Time Counter (RTC). 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. Setting
AS2 and resetting EXCLK enables the TOSC oscillator.
For Timer/Counter2, the possible prescaled selections are: clk
clk
selected. Setting the PSR2 bit in GTCCR resets the prescaler. This allows the user to
operate with a predictable prescaler.
• Bit 1 – PSR2: 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 “Bit 7
– TSM: Timer/Counter Synchronization Mode” on page 93 for a description of the
Timer/Counter Synchronization mode.
Bit
Read/Write
Initial Value
T2S
TOSC2
TOSC1
/128, clk
AS2
TSM
R/W
T2S
7
0
Oscillator
32 kHz
Enable
/256, and clk
EXCLK
PSR2
CS20
CS21
CS22
EXCLK
R
6
–
0
clk
0
1
I/O
IO
AS2
. By setting the AS2 bit in ASSR, Timer/Counter2 is asyn-
T2S
R
5
–
0
/1024. Additionally, clk
0
1
clk
T2S
R
4
–
0
Clear
R
3
–
0
T2S
TIMER/COUNTER2 CLOCK SOURCE
. clk
0
T2S
T2S
10-BIT T/C PRESCALER
R
2
–
0
as well as 0 (stop) may be
clk
is by default connected to
AT90CAN128
T2S
T2
PSR2
/8, clk
R/W
1
0
T2S
PSR310
R/W
/32, clk
0
0
GTCCR
T2S
/64,
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