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參數資料
| 型號： | W77E468 |
| 廠商： | WINBOND ELECTRONICS CORP |
| 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： | 50/84頁 |
| 文件大小： | 531K |
| 代理商： | W77E468 |
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Preliminary W77E468
- 50 -
External Reset
The device continuously samples the RST pin at state C4 of every machine cycle. Therefore the RST
pin must be held for at least 2 machine cycles to ensure detection of a valid RST high. The reset
circuitry then synchronously applies the internal reset signal. Thus the reset is a synchronous
operation and requires the clock to be running to cause an external reset.
Once the device is in reset condition, it will remain so as long as RST is 1. Even after RST is
deactivated, the device will continue to be in reset state for up to two machine cycles, and then begin
program execution from 0000h. There is no flag associated with the external reset condition. However
since the other two reset sources have flags, the external reset can be considered as the default reset
if those two flags are cleared.
Watchdog Timer Reset
The Watchdog timer is a free running timer with programmable time-out intervals. The user can clear
the watchdog timer at any time, causing it to restart the count. When the time-out interval is reached
an interrupt flag is set. If the Watchdog reset is enabled and the watchdog timer is not cleared, then
512 clocks from the flag being set, the watchdog timer will generate a reset . This places the device
into the reset condition. The reset condition is maintained by hardware for two machine cycles. Once
the reset is removed the device will begin execution from 0000h.
RESET STATE
Most of the SFRs and registers on the device will go to the same condition in the reset state. The
Program Counter is forced to 0000h and is held there as long as the reset condition is applied.
However, the reset state does not affect the on-chip RAM. The data in the RAM will be preserved
during the reset. However, the stack pointer is reset to 07h, and therefore the stack contents will be
lost. The RAM contents will be lost if the V
DD
falls below approximately 2V, as this is the minimum
voltage level required for the RAM to operate normally. Therefore after a first time power on reset the
RAM contents will be indeterminate. During a power fail condition, if the power falls below 2V, the
RAM contents are lost. After a reset most SFRs are cleared. Interrupts and Timers are disabled. The
Watchdog timer is disabled if the reset source was a POR. The port SFRs have FFh written into them
which puts the port pins in a high state. Port 0 floats as it does not have on-chip pull-ups.
Table 6. SFR Reset Value
SFR Name
P0
SP
DPL
DPH
DPL1
DPH1
DPS
PCON
TCON
TMOD
TL0
TL1
Reset Value
11111111b
00000111b
00000000b
00000000b
00000000b
00000000b
00000000b
00xx0000b
00000000b
00000000b
00000000b
00000000b
SFR Name
IE
SADDR
P3
IP
SADEN
T2CON
T2MOD
RCAP2L
RCAP2H
TL2
TH2
TA
Reset Value
00000000b
00000000b
11111111b
x0000000b
00000000b
00000000b
00000x00b
00000000b
00000000b
00000000b
00000000b
11111111b
相關PDF資料 |
PDF描述 |
|---|---|
| W77E516 | 8-BIT MICROCONTROLLER |
| W77E516-25 | 8-BIT MICROCONTROLLER |
| W77E516-40 | 8-BIT MICROCONTROLLER |
| W77E516F-25 | 8-BIT MICROCONTROLLER |
| W77E516F-40 | 8-BIT MICROCONTROLLER |
相關代理商/技術參數 |
參數描述 |
|---|---|
| W77E468F-25 | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8 BIT MICROCONTROLLER |
| W77E468F-40 | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8 BIT MICROCONTROLLER |
| W77E516 | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W77E516-25 | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W77E516-40 | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
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