Getting Started

Chapter 4: C Types, Operators, and Expressions

Figure 12: from page 92 of the ATMega169 data book

Fast PWM mode and CLK/256 prescaler

TCCR0A |= (1<<WGM01)|(1<<WGM00)|(4<<CS00);

We use the left shift o number before the operand to the
numeric position in th the number following the operand. In
the case of (1<<WGM01) we shift a 1 to the left by WGM01 bit positions, and we
see from iom169.h:

#define FOC0A 7

#defin

#defin

#defin

#defin

#defin

#defin 1

Let’s initialize the timer with:

// Set

perator ’<<’ to shif

ed by

t the

e byte specifi

/* TCCR0A */

e WGM00 6

e COM0A1 5

e COM0A0 4

e WGM01 3

e CS02 2

e CS01

#define CS00 0

WGM01 = 3, so (1<<WGM01) is the same as (1<<3) and means to shift 0000001
three places left to 00001000. Now look at The TCCR0A register and notice
where the WGM01 bit is located. Ah ha! Like I said, we have a way of dealing
with a bit by a name.