3 time base timer (tbt), Toshiba – Toshiba TMP87CP24AF User Manual
Page 62
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TOSHIBA
TMP87CM24A/P24A
2.3
Time Base Timer (TBT)
The
time-base
timer
is
used
to
generate
the
base
time
for
key
scan
and
dynamic
display
processing.
For
this purpose, it generates a time-base timer interrupt (INTTBT) at predetermined intervals.
This
interrupt
is
generated
beginning
with
the
first
rising
edge
of
the
source
clock
(the
timing
generator's
divider
output
selected
by
TBTCK)
after
the
time-base
timer
is
enabled.
Note
that
since
the
divider
cannot
be
cleared
by
a
program,
the
first
interrupt
only
may
occur
earlier
than
the
set
interrupt
period. (See Figure 2-10. (b).)
When
selecting
the
interrupt
frequency,
make
sure
the
time-base
timer
is
disabled.
(Do
not
change
the
selected
interrupt
frequency
when
disabling
the
active
timer
either.)
However,
you
can
select
the
interrupt frequency simultaneously when enabling the timer.
Example : Sets the time base timer frequency to fc/2i6[Hz] and enables an INTTBT interrupt.
LD
(TBTCR), 00001010B
SET
(EIRL). 6
Figure 2-10. Time Base Timer
7
6 5
4
3
2
1
0
(DVOEN)
(DVOCK)
(DV7CK)
TBTEN
,TBTCK ,
TBTCR
(0036
h
)
(Initial value :
0**0 0***)
TBTEN
Time base timer
0
Disable
enable/disable
1
Enable
000
fc/223 or fs/2^^[Hz]
001
fc/22^ or fs/2^3
R/W
010
fc/2^^ or fs/2^
TBTCK
Time base timer interrupt
oil
fc/2^^ or fs/2^
fc/2^3 or fs/2^
frequency select
100
101
fc/2^2 or fs/2'^
110
fc/2" or fs/2^
111
fc/2^ or fs/2
Note:
fc: High-frequency clock [Hz], fs: Low-frequency clock [Hz], *: Don't care
Figure 2-11. Time Base Timer Control Register
3
-
24-62
2002
-
10-03