HT48RA0A Ver la hoja de datos (PDF) - Holtek Semiconductor
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HT48RA0A Datasheet PDF : 31 Pages
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HT48RA0A
Reset
There are three ways in which a reset can occur:
· RES reset during normal operation
· RES reset during HALT
· WDT time-out reset during normal operation
Some registers remain unchanged during reset condi-
tions. Most registers are reset to the ²initial condition²
when the reset conditions are met. By examining the PD
and TO flags, the program can distinguish between dif-
ferent ²chip resets².
TO PD
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
Note: ²u² means unchanged.
To guarantee that the system oscillator has started and
stabilized, the SST (System Start-up Timer) provides an
extra-delay of 1024 system clock pulses when the sys-
tem powers up or when the system awakes from a HALT
state.
When a system power up occurs, an SST delay is added
during the reset period. But when the reset comes from
the RES pin, the SST delay is disabled. Any wake-up
from HALT will enable the SST delay.
The functional unit chip reset status is shown below.
PC
WDT Prescaler
Input/Output ports
SP
Carrier output
000H
Clear
Input mode
Points to the top of the stack
Low level
VDD
RES
S S T T im e - o u t
C h ip R e s e t
tS S T
Reset timing chart
V DD
RES
Reset circuit
H A LT
W DT W DT
T im e - o u t
R eset
RES
O SC1
SST
1 0 -s ta g e
R ip p le C o u n te r
P o w e r - o n D e te c tio n
Reset configuration
R eset
The chip reset status of the registers is summarized in the following table:
Register
Reset
(Power On)
WDT Time-out
(Normal Operation)
RES Reset
(Normal Operation)
PC (Program Counter)
000H
000H
000H
MP
-xxx xxxx
-uuu uuuu
-uuu uuuu
ACC
xxxx xxxx
uuuu uuuu
uuuu uuuu
TBLP
xxxx xxxx
uuuu uuuu
uuuu uuuu
TBLH
--xx xxxx
--uu uuuu
--uu uuuu
STATUS
--00 xxxx
--1u uuuu
--uu uuuu
PA
1111 1111
1111 1111
1111 1111
PB
1111 1111
1111 1111
1111 1111
PC
---- ---1
---- ---1
---- ---1
Note: ²u² means unchanged
²x² means unknown
RES Reset
(HALT)
000H
-uuu uuuu
uuuu uuuu
uuuu uuuu
--uu uuuu
--01 uuuu
1111 1111
1111 1111
---- ---1
Rev. 1.70
8
July 16, 2003
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