Datasheet

19. 8-bit Timer/Counter0
19.1 Features
• Single Channel Counter
• Frequency Generator
• External Event Counter
• 10-bit Clock Prescaler
19.2 Overview
Timer/Counter0 is a general purpose, single channel, 8-bit Timer/Counter module. A simplified block
diagram of the 8-bit Timer/Counter is shown in the figure below. For the actual placement of I/O pins,
refer to Pin Configurations. CPU accessible I/O Registers, including I/O bits and I/O pins, are shown in
bold. The device-specific I/O Register and bit locations are listed in the Register Description.
Figure 19-1. 8-bit Timer/Counter Block Diagram
Timer/Counter
DATA BUS
TCNTn
Control Logic
= 0xFF
count
TOVn
(Int.Req.)
TCCRn
Clock Select
Tn
Edge
Detector
( From Prescaler )
clk
Tn
Related Links
Pin Configurations
19.2.1 Registers
The Timer/Counter (TCNT0) is an 8-bit register. Interrupt request (abbreviated to Int. Req. in the figure)
signals are all visible in the Timer Interrupt Flag Register (TIFR). All interrupts are individually masked
with the Timer Interrupt Mask Register (TIMSK). TIFR and TIMSK are not shown in the figure since these
registers are shared by other timer units.
The Timer/Counter can be clocked internally or via the prescaler, or by an external clock source on the T0
pin. The Clock Select logic block controls which clock source and edge the Timer/Counter uses to
increment its value. The Timer/Counter is inactive when no clock source is selected. The output from the
clock select logic is referred to as the timer clock (clk
T0
).
AVR 8-Bit Microcontroller
8-bit Timer/Counter0
© 2017 Microchip Technology Inc.
Datasheet Complete
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