ATMEGA64_08 Datasheet, PDF (147/393 Pages) ATMEL Corporation – 8-bit Microcontroller with 64K Bytes In-System Programmable Flash

Definitions
Timer/Counter
Clock Sources
ATmega64(L)
ate a PWM or variable frequency output on the Output Compare pin (OC2). For details, see
“Output Compare Unit” on page 148. The Compare Match event will also set the Compare Flag
(OCF2) which can be used to generate an Output Compare interrupt request.
Many register and bit references in this document are written in general form. A lower case “n”
replaces the Timer/Counter number, in this case 2. However, when using the register or bit
defines in a program, the precise form must be used (i.e., TCNT2 for accessing Timer/Counter2
counter value and so on).
The definitions in Table 63 are also used extensively throughout this section.
Table 63. Definitions
BOTTOM The counter reaches the BOTTOM when it becomes 0x00.
MAX
The counter reaches its MAXimum when it becomes 0xFF (decimal 255).
TOP
The counter reaches the TOP when it becomes equal to the highest
value in the count sequence. The TOP value can be assigned to be the
fixed value 0xFF (MAX) or the value stored in the OCR2 Register. The
assignment is dependent on the mode of operation.
The Timer/Counter can be clocked by an internal or an external clock source. The clock source
is selected by the Clock Select logic which is controlled by the Clock Select (CS22:0) bits
located in the Timer/Counter Control Register (TCCR2). For details on clock sources and pres-
caler, see “Timer/Counter3, Timer/Counter2 and Timer/Counter1 Prescalers” on page 144.
2490N–AVR–05/08
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