Chapter 4: C Types, Operators, and Expressions
While using &= and/or |= is acceptable, the Butterfly code generally does this a
ake the code a little clearer,
first. When we create masks to set or clear bits,
ed PD0 and we
h ighth bit simple, but it gets hairy when
give com es to all the bits in the dozens of registers. For instance
e Time TCC imer e
owing b age 90 ATMEGA
‘a’ = 0x61 = 01100001
~0x20 = 11011111
AND = 01000001 = 0x41 = ‘A’
This is a lot harder for us than ordinary subtraction, but much easier for the
machine.
little differently, not to make your life harder, but to m
though it won’t seem that way at
we will nam or instance the
can guess t
e the bits so f
at the efirst bit in port D is nam
is named PD7. That’s
we plicated nam
in th r0 register:
its named (p
R0A, T /Counter Control Register A we have th
foll 169 databook):
Bit 7 = FOC0A – Force Output Compare A
rm Generation Mode 0
as:Bit 6 = WGM00 – Wavefo
Bit 5 = COM0A1 – Compare Match Output Mode 1
Bit 4 = COM0A0 – Compare Match Output Mode 0
Bit 3 = WGM01 – Waveform Generation Mode 1
Bit 2 = CS02 – Clock Select Bit 2
Bit 1 = CS01 – Clock Select Bit 1
Bit 0 = CS00 – Clock Select Bit 0
Bits 0, 1, and 2 the Clock Select Bits are defined