HT46R53A/HT46R54A
The WDT time-out during HALT differs from other chip
reset conditions, for it can perform a ²warm reset² that
resets only the Program Counter and SP, leaving the
other circuits at their original state. Some registers re-
main unaffected during any other reset conditions. Most
registers are reset to the ²initial condition² when the re-
set conditions are met. Examining the PDF and TO
flags, the program can distinguish between different
²chip resets².
TO PDF
RESET Conditions
0 0 RES reset during power-up
u u RES reset during normal operation
0 1 RES wake-up HALT
1 u WDT time-out during normal operation
1 1 WDT wake-up HALT
Note: ²u² stands for ²unchanged²
To guarantee that the system oscillator is started and
stabilized, the SST (System Start-up Timer) provides an
extra-delay of 1024 system clock pulses when the sys-
tem reset (power-up, WDT time-out or RES reset) or the
system awakes from the HALT state. When a system re-
set occurs, the SST delay is added during the reset pe-
riod. Any wake-up from the HALT will enable the SST
delay. An extra option load time delay is added during
system reset (Power-up, WDT time-out at normal mode
or RES reset).
The functional unit chip reset status are shown below.
Program Counter
000H
Interrupt
Disable
Prescaler, Divider Cleared
WDT
Clear. After master reset,
WDT begins counting
Timer/Event Counter Off
Input/Output Ports Input mode
Stack Pointer
Points to the top of the stack
V DD
0 .0 1 m F *
100kW
RES
10kW
0 .1 m F *
Reset Circuit
Note:
²*² Make the length of the wiring, which is con-
nected to the RES pin as short as possible, to
avoid noise interference.
VDD
RES
S S T T im e - o u t
tS S T + tO P D
C h ip R e s e t
Reset Timing Chart
H A LT
W DT
W DT
T im e - o u t
R eset
RES
E x te rn a l
O SC1
SST
1 0 - b it R ip p le
C o u n te r
W a rm R e s e t
C o ld
R eset
P o w e r - o n D e te c tio n
Reset Configuration
Rev. 1.00
13
August 24, 2006