
99
7682C–AUTO–04/08
AT90CAN32/64/128
12. 8-bit Timer/Counter0 with PWM
Timer/Counter0 is a general purpose, single channel, 8-bit Timer/Counter module. The main
features are:
12.1
Features
Single Channel Counter
Clear Timer on Compare Match (Auto Reload)
Glitch-free, Phase Correct Pulse Width Modulator (PWM)
Frequency Generator
External Event Counter
10-bit Clock Prescaler
Overflow and Compare Match Interrupt Sources (TOV0 and OCF0A)
12.2
Overview
Many register and bit references in this section 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.
A lower case “x” replaces the Output Compare unit channel, in this case A. However, when
using the register or bit defines in a program, the precise form must be used, i.e., OCR0A for
accessing Timer/Counter0 output compare channel A value and so on.
A simplified block diagram of the 8-bit Timer/Counter is shown in
Figure 12-1. For the actual
placement of I/O pins, refer to “Pinout AT90CAN32/64/128 - TQFP” on page 5. CPU accessible
I/O Registers, including I/O bits and I/O pins, are shown in bold. The device-specific I/O Register
Figure 12-1. 8-bit Timer/Counter Block Diagram
Timer/Counter
DA
T
A
BUS
=
TCNTn
Waveform
Generation
OCnx
=
0
Control
Logic
=
0xFF
BOTTOM
count
clear
direction
TOVn
(Int.Req.)
OCRnx
TCCRn
Clock
Select
Tn
Edge
Detector
(
From
Prescaler
)
clk
Tn
TOP
OCn
(Int.Req.)