HT49R30A-1/HT49C30-1/HT49C30L
Rev. 1.10
14
September 25, 2002
external reset (a low level to RES), software instruction,
and a HALT instruction. There are two types of soft-
ware instructions; CLR WDT and the other set
CLR
WDT1 and CLR WDT2 . Of these two types of instruc-
tion, only one type of instruction can be active at a time
depending on the options
CLR WDT times selection
option . If the CLR WDT is selected (i.e., CLR WDT
times equal one), any execution of the CLR WDT in-
struction clears the WDT. In the case that CLR WDT1
and CLR WDT2 are chosen (i.e., CLR WDT times
equal two), these two instructions have to be executed
to clear the WDT; otherwise, the WDT may reset the
chip due to time-out.
Multi-function timer
The device provides a multi-function timer for the WDT,
time base and RTC but with different time-out periods.
The multi-function timer consists of a 8-stage divider
and an 7-bit prescaler, with the clock source coming
from the WDT OSC or RTC OSC or the instruction clock
(i.e.., system clock divided by 4). The multi-function
timer also provides a selectable frequency signal
(ranges from f
S
/2
2
to f
S
/2
8
) for LCD driver circuits, and a
selectable frequency signal (ranges from f
S
/2
2
to f
S
/2
9
)
for the buzzer output by options. It is recommended to
select a near 4kHz signal to LCD driver circuits for
proper display.
Time base
The time base offers a periodic time-out period to gener-
ate a regular internal interrupt. Its time-out period
ranges from /2
12
to f
S
/2
15
selected by options. If time
base time-out occurs, the related interrupt request flag
(TBF; bit 4 of INTC1) is set. But if the interrupt is en-
abled, and the stack is not full, a subroutine call to loca-
tion 10H occurs.
Real time clock
RTC
The real time clock (RTC) is operated in the same man-
ner as the time base that is used to supply a regular in-
ternal 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 5 of INTC1) is set. But if
the interrupt is enabled, and the stack is not full, a sub-
routine call to location 14H occurs. The real time clock
time-out signal also can be applied to be a clock source
of timer/event counter for getting a longer time-out pe-
riod.
' ' ' ' ' ' ' '
&
' *
'
& )
/ & )
3
*
B B
' 7 & )
/ & )
6
9
$
'
A
' 7 & )
/ & )
2
9
A
=
Time base
A
' ' ' ' ' ' ' '
&
2 '
'
: D
=
(
'
& )
2
/ & )
3
Real time clock
'
=
> )
A
-
'
=
=
-
> 4 B
0 5 2 4 B
1
1
&
;
'
' & )
3
/ & )
5
A
Watchdog Timer