參數(shù)資料
型號: HT48R51-2(40DIP-A0)
元件分類: 8位微控制器
英文描述: 8-BIT MICROCONTROLLER
中文描述: 8位微控制器
文件頁數(shù): 13/42頁
文件大?。?/td> 259K
代理商: HT48R51-2(40DIP-A0)
HT48R50A-1/HT48C50-1
Rev. 1.00
13
January 2, 2003
nal on port A or a WDT overflow. An external reset
causes a device initialization and the WDT overflow per-
forms a warm reset . After the TO and PD flags are ex-
amined, the reason for chip reset can be determined.
The PD flag is cleared by system power-up or executing
the CLR WDT instruction and is set when executing
the HALT instruction. The TO flag is set if the WDT
time-out occurs, and causes a wake-up that only resets
thePCandSP;theothersremainintheiroriginalstatus.
The port A wake-up and interrupt methods can be con-
sidered as a continuation of normal execution. Each bit
in port A can be independently selected to wake up the
device by options. Awakening from an I/O port stimulus,
the program will resume execution of the next instruc-
tion. If it awakens from an interrupt, two sequence may
occur. If the related interrupt is disabled or the interrupt
is enabled but the stack is full, the program will resume
execution at the next instruction. If the interrupt is en-
abled and the stack is not full, the regular interrupt re-
sponse takes place. If an interrupt request flag is set to
1 before entering the HALT mode, the wake-up func-
tion of the related interrupt will be disabled. Once a
wake-up event occurs, it takes 1024 t
SYS
(system clock
period) to resume normal operation. In other words, a
dummy period will be inserted after a wake-up. If the
wake-up results from an interrupt acknowledge signal,
the actual interrupt subroutine execution will be delayed
by one or more cycles. If the wake-up results in the next
instruction execution, this will be executed immediately
after the dummy period is finished.
To minimize power consumption, all the I/O pins should
be carefully managed before entering the HALT status.
The RTC oscillator still runs in the HALT mode (if the
RTC oscillator is enabled).
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
The WDT time-out during HALT is different from other
chip reset conditions, since it can perform a warm re -
set thatresetsonlythePCandSP,leavingtheothercir-
cuits in their original state. Some registers remain un-
changed during other reset conditions. Most registers
are reset to the initial condition when the reset condi-
tions are met. By examining the PD and TO flags, the
programcandistinguishbetweendifferent chipresets .
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
1
1
WDT wake-up HALT
Note: u stands for 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.
PC
000H
Interrupt
Disable
Prescaler
Clear
WDT
Clear. After master reset,
WDT begins counting
Timer/Event Counter
Off
Input/Output Ports
Input mode
SP
Points to the top of the stack
Reset circuit
,
*
!
,
$ (
'
!
&
!
*
!
; > # ! *
# " "
!
Reset configuration
!
* #
;
!
) # " * *
!
Reset timing chart
相關PDF資料
PDF描述
HT48RA0(20DIP-A) 8-BIT MICROCONTROLLER
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