ATMEGA8535L-8AC Atmel, ATMEGA8535L-8AC Datasheet - Page 72

• Manufacturer Part Number: ATMEGA8535L-8AC
• Description: IC AVR MCU 8K LV 8MHZ COM 44TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA8535L-8AC

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 8MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 8KB (4K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 44-TQFP, 44-VQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Definitions
Timer/Counter Clock
Sources
Counter Unit
72
ATmega8535(L)
The double buffered Output Compare Register (OCR0) is compared with the
Timer/Counter value at all times. The result of the compare can be used by the Wave-
form Generator to generate a PWM or variable frequency output on the Output Compare
pin (OC0). See “Output Compare Unit” on page 73. for details. The Compare Match
event will also set the Compare Flag (OCF0) 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 0. However, when using the
register or bit defines in a program, the precise form must be used, i.e., TCNT0 for
accessing Timer/Counter0 counter value and so on.
The definitions in Table 38 are also used extensively throughout the document.
Table 38. Definitions
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
(CS02:0) bits located in the Timer/Counter Control Register (TCCR0). For details on
clock sources and prescaler, see “Timer/Counter0 and Timer/Counter1 Prescalers” on
page 87.
The main part of the 8-bit Timer/Counter is the programmable bi-directional counter unit.
Figure 28 shows a block diagram of the counter and its surroundings.
Figure 28. Counter Unit Block Diagram
Signal description (internal signals):
BOTTOM
MAX
TOP
count
direction
clear
clk
Tn
DATA BUS
TCNTn
The counter reaches the BOTTOM when it becomes 0x00.
The counter reaches its MAXimum when it becomes 0xFF (decimal 255).
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 OCR0 Register. The
assignment is dependent on the mode of operation.
Increment or decrement TCNT0 by 1.
Select between increment and decrement.
Clear TCNT0 (set all bits to zero).
Timer/Counter clock, referred to as clk
direction
count
clear
bottom
Control Logic
top
TOVn
(Int.Req.)
clk
Tn
T0
in the following.
Clock Select
( From Prescaler )
Detector
Edge
2502K–AVR–10/06
Tn