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參數(shù)資料
| 型號(hào)： | W78L51F-24 |
| 廠商： | WINBOND ELECTRONICS CORP |
| 元件分類： | 微控制器/微處理器 |
| 英文描述： | 8-BIT MICROCONTROLLER |
| 中文描述： | 8-BIT, MROM, 24 MHz, MICROCONTROLLER, PQFP44 |
| 封裝： | QFP-44 |
| 文件頁(yè)數(shù)： | 7/18頁(yè) |
| 文件大?。?/td> | 256K |
| 代理商： | W78L51F-24 |
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W78L51
Publication Release Date: January 1999
- 7 -
Revision A2
2. PORT4
Another bit-addressable port P4 is also available and only 4 bits (P4<3:0>) can be used. This port
address is located at 0D8H with the same function as that of port P1, except the P4.3 and P4.2 are
alternative function pins. It can be used as general I/O pins or external interrupt input sources (
INT2
/
INT3 ).
Example: P4
REG
0D8H
MOV
P4, #0AH
; Output data "A" through P4.0
P4.3.
MOV
A, P4
; Read P4 status to Accumulator.
SETB
P4.0
; Set bit P4.0
CLR
P4.1
; Clear bit P4.1
Watchdog Timer
The Watchdog timer is a free-running timer which can be programmed by the user to serve as a
system monitor, a time-base generator or an event timer. It is basically a set of dividers that divide
the system clock. The divider output is selectable and determines the time-out interval. When the
time-out occurs a flag is set, and a system reset can also be caused if it is enabled. The main use of
the Watchdog timer is as a system monitor. This is important in real-time control applications. In case
of power glitches or electro-magnetic interference, the processor may begin to execute errant code. If
this is left unchecked the entire system may crash. The watchdog time-out selection will result in
different time-out values depending on the clock speed. The Watchdog timer will de disabled on
reset. In general, software should restart the Watchdog timer to put it into a known state. The control
bits that support the Watchdog timer are discussed below.
Watchdog Timer Control Register
Bit:
7
6
5
4
-
3
-
2
1
0
ENW
CLRW
WIDL
PS2
PS1
PS0
Mnemonic: WDTC
Address: 8FH
ENW : Enable watch-dog if set.
CLRW : Clear watch-dog timer and prescaler if set. This flag will be cleared automatically
WIDL : If this bit is set, watch-dog is enabled under IDLE mode. If cleared, watch-dog is disabled
under IDLE mode. Default is cleared.
PS2, PS1, PS0 : Watch-dog prescaler timer select. Prescaler is selected when set PS2~0 as follows:
PS2 PS1 PS0
0 0 0
0 1 0
0 0 1
0 1 1
1 0 0
1 0 1
1 1 0
1 1 1
PRESCALER SELECT
2
4
8
16
32
64
128
256
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| W78L51 | 8-BIT MICROCONTROLLER |
| W78L51-24 | 8-BIT MICROCONTROLLER |
| W78L51P-24 | 8-BIT MICROCONTROLLER |
| W78C052D | 8-BIT MICROCONTROLLER |
| W78C052D40DL | 8-BIT MICROCONTROLLER |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| W78L51P-24 | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W78L52 | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W78L52-24 | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W78L52F-24 | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
| W78L52P-24 | 制造商:WINBOND 制造商全稱:Winbond 功能描述:8-BIT MICROCONTROLLER |
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