HT46RU22 Holtek Semiconductor Inc., HT46RU22 Datasheet - Page 13

• Manufacturer Part Number: HT46RU22
• Description: Ht46ru22 -- A/d Type 8-bit Mcu
• Manufacturer: Holtek Semiconductor Inc.

Reset
There are three ways in which a reset can occur:
The WDT time-out during HALT is different from other
chip reset conditions, since it can perform a warm re -
set 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 initial condition when
the reset conditions are met. By examining the PDF and
TO flags, the program can distinguish between different
Note: u means unchanged
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 reset occurs, the SST delay is added
during the reset period. Any wake-up from HALT will en-
able 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.
Rev. 1.20
chip resets .
Program Counter
Interrupt
WDT
Timer/Event Counter
Input/Output ports
Stack Pointer
TO PDF
RES reset during normal operation
RES reset during HALT
WDT time-out reset during normal operation
0
u
0
1
1
0
u
1
u
1
RES reset during power-up
RES reset during normal operation
RES wake-up HALT
WDT time-out during normal operation
WDT wake-up HALT
RESET Conditions
000H
Disable
Clear after master reset,
WDT begins counting
Off
Input mode
Points to the top of the stack
13
Note:
nected to the RES pin as short as possible, to
avoid noise interference.
* Make the length of the wiring, which is con-
Reset Timing Chart
Reset Configuration
Reset Circuit
HT46RU22
March 23, 2007