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Electronics Tutorial for Beginners
ABC of Electronics Offering free comprehensive basic
electronics tutorial. In this Electronics Tutorial we
have explained the basic electronic concepts. Here you
can find 8051 Tutorials & 555 Timer Tutorials which are
commonly used in electronics.
Every effort is made
to keep the website up and running smoothly |
8051 Timer
Basics
8051 has two
timers T0(P
3.4) and
T1(P 3.5).
Timers can
be used for
generating
time delays
or as
counters as
well ,for
that we have
to provide
the pulses
externally.
|
SFR
Type |
Description
of
SFR |
SFR
Address
|
|
TH0
|
High
Byte
OF
Timer
0 |
8Ch
|
|
TL0
|
Low
Byte
OF
Timer
0 |
8Ah
|
|
TH1
|
High
Byte
OF
Timer
1 |
8Dh
|
|
TL1
|
Low
Byte
OF
Timer
1 |
8Bh
|
|
TCON
|
Timer
Control
|
88h
|
|
TMOD
|
Timer
Mode
|
89h
|
TMOD
SFR
-Timers
By
Using
this
SFR
we
can
modify
timer
to
be a
16-bit
timer,
an
8-bit
auto
reload
timer,
a
13-bit
timer,
or 2
separate
timers.
In
16
bit
mode
the
timer
ranges
from
0000-ffffh
and
on
roll
over
sets
the
tf
flag
whereas
in
the
8
bit
auto
reload
mode
the
timer
ranges
from
00-ffh
and
sets
the
tf
flag
here
as
well
on
roll
over.
In
auto
reload
mode
we
don't
have
to
reload
the
the
values
of
th
and
tl
registers
like
we
did
it
in
the
16
bit
mode.
|
Bit
Number |
Type |
Working |
Timer
Type |
|
7
|
GATE1
|
Gating
Control
when
set |
1
|
|
6
|
C/T1
|
To
decide
whether
timer
is
used
as a
delay
generator
or
as
an
event
counter |
1
|
|
5
|
M1
|
Timer
mode
bit |
1
|
|
4
|
M0
|
Timer
mode
bit |
1
|
|
3
|
GATE0
|
Gating
Control
Purpose |
0
|
|
2
|
C/T0
|
To
decide
whether
timer
is
used
as a
delay
generator
or
as
an
event
counter |
0
|
|
1
|
M1
|
Timer
mode
bit |
0
|
|
0
|
M0
|
Timer
mode
bit
|
0
|
|
M1
|
M0
|
Timer
Mode
|
Description
of
Mode
|
|
0
|
0
|
0
|
13-bit
Timer.
|
|
0
|
1
|
1
|
16-bit
Timer
|
|
1
|
0
|
2
|
8-bit
auto-reload
|
|
1
|
1
|
3
|
Split
timer
mode
|
TCON
SFR-Timers-
TCON
REGISTER is
the register
where we
have the
tr0,tr1,tf0,tf1
bits.
tr0, tr1
( timer run)
for timer 0
and timer 1
and
tf0,tf1(timer
overflow)
for timer 0
and timer 1
respectively.
The
Timer
Control SFR
is used to
modify the
way in which
the 8051's
two timers
T0 & T1 are
operating.
|
Bit
|
Type |
Working |
|
7
|
TF1
|
Timer
1
Overflow
flag
|
|
6
|
TR1
|
Timer
1
Run
control
bit |
|
5
|
TF0
|
Timer
0
Overflow
flag
|
|
4
|
TR0
|
Timer
0
Run
control
bit |
|
3 |
IE1 |
External
Interrupt
1 |
|
2 |
IT1 |
Interrupt
1
type |
|
1 |
IE0 |
External
Interrupt
0 |
|
0 |
IT0 |
Interrupt
0
Type |
|
|
|
|
|
|
|
|
|
© Copyright 2008, ABC of Electronics. All Rights Reserved.
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