Author :
Craig
Steiner
Source :
8052.com
Book :
The
8051/8052
Microcontroller:
Architecture,
Assembly
Language,
And
Hardware
Interfacing
(Paperback)
TIMER 2 AS A BAUD-RATE GENERATOR
Timer 2
may be
used as
a baud
rate
generator.
This is
accomplished
by
setting
either
RCLK
(T2CON.5)
or TCLK
(T2CON.4).
With the
standard
8051,
Timer 1
is the
only
timer
which
may be
used to
determine
the baud
rate
of the
serial
port.
Additionally,
the
receive
and
transmit
baud
rate
must be
the
same.
With the
8052,
however,
the user
may
configure
the
serial
port to
receive
at one
baud
rate and
transmit
with
another.
For
example,
if RCLK
is set
and TCLK
is
cleared,
serial
data
will be
received
at the
baud
rate
determined
by Timer
2
whereas
the baud
rate of
transmitted
data
will be
determined
by Timer
1.
Determining
the
auto-reload
values
for a
specific
baud
rate is
discussed
in
Serial
Port
Operation;
the only
difference
is that
in the
case of
Timer 2,
the
auto-reload
value is
placed
in
RCAP2H
and
RCAP2L,
and the
value is
a 16-bit
value
rather
than an
8-bit
value.
NOTE:
When
Timer 2
is used
as a
baud
rate
generator
(either
TCLK or
RCLK are
set),
the
Timer 2
Overflow
Flag
(TF2)
will not
be set.
