HT46R12
Reset
The functional unit chip reset status are shown below.
There are three ways in which a reset can occur:
Program Counter
Interrupt
000H
·
·
·
RES reset during normal operation
RES reset during HALT
Disable
Cleared
Prescaler, Divider
WDT time-out reset during normal operation
Clear. After master reset,
WDT begins counting
WDT
The WDT time-out during HALT is different from other
chip reset conditions, since it can perform a ²warm re -
set² that resets only the program counter and SP, leav-
ing the other circuits in their original state. Some regis-
ters remain unchanged during other reset conditions.
Most registers are reset to the ²initial condition² when
the reset conditions are met. By examining the PDF and
TO flags, the program can distinguish between different
²chip resets².
Timer/Event Counter Off
PPG Timer
Off
PPG output
Floating
Input/Output Ports
Stack Pointer
Input mode
Points to the top of the stack
TO PDF
RESET Conditions
RES reset during power-up
RES reset during normal operation
RES wake-up HALT
V
D
D
0
u
0
1
1
0
u
1
u
1
m
0 . 0 1 F *
1
0
0
k
R
E
S
WDT time-out during normal operation
WDT wake-up HALT
1
0
k
m
0 . 1 F *
Note: ²u² means unchanged
Reset Circuit
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.
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.
When a system reset occurs, the SST delay is added
during the reset period. Any wake-up from HALT will en-
able the SST delay.
H
A
L
T
W
a
r
m
R
e
s
e
t
W
D
T
An extra option load time delay is added during a system
reset (power-up, WDT time-out at normal mode or RES
reset).
R
E
S
C
o
l
d
R
e
s
e
t
V
D
D
S
S
T
1
0
-
b
i
t
R
i
p
p
l
e
O
S
C
1
R
E
S
t
S
S
T
C
o
u
n
t
e
r
S
S
T
T
i
m
e
-
o
u
t
S
y
s
t
e
m
R
e
s
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C
h
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Reset Configuration
Reset Timing Chart
Rev. 1.20
13
February 24, 2006
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
