HT49R50
18
October 22, 1999
Time base
The time base offers a periodic time-out period
to generate a regular internal interrupt. Its
time-out period ranges from f
S
/2
12
to f
S
/2
15
se-
lected by options. If time base time-out occurs,
the related interrupt request flag (TBF; bit 5 of
INTC1) is set. But if the interrupt is enabled,
and the stack is not full, a subroutine call to lo-
cation 14H occurs. The time base time-out sig-
nal also can be applied to be a clock source of
timer/event counter 1 for getting a longer
timer-out period.
Real time clock
RTC
The real time clock (RTC) is operated in the
same manner as the time base that is used to
supply a regular internal interrupt. Its
time-out period ranges from f
S
/2
8
to f
S
/2
15
by
software programming . Writing data to RT2,
RT1 and RT0 (bit2, 1, 0 of RTCC;09H) yields
various time-out periods. If the RTC time-out
occurs, the related interrupt request flag (RTF;
bit 6 of INTC1) is set. But if the interrupt is en-
abled, and the stack is not full, a subroutine call
to location 18H occurs. The real time clock
time-out signal also can be applied to be a clock
source of timer/event counter 0 for getting a
longer time-out period.
RT2
RT1
RT0
RTC Clock Divided
Factor
2
8
2
9
2
10
2
11
2
12
2
13
2
14
2
15
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
Power down operation
HALT
The HALT mode is initialized by the "HALT"
instruction and results in the following.
The system oscillator turns off but the WDT
oscillator keeps running (if the WDT oscilla-
tor or the real time clock is selected).
The contents of the on-chip RAM and of the
registers remain unchanged.
The WDT is cleared and start recounting (if
the WDT clock source is from the WDT oscil-
lator or the real time clock oscillator).
% % % % % % % %
$
=
<
% (
%
$ '
+ $ '
2
= %
( @ @% 6 $
'
+ $ '
5
8
" %
'
+ $ '
4
8
Time base
% % % % % % % %
$
4 %
9 D
<
&
%
$ '
4
+ $ '
2
Real time clock