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參數(shù)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(shù)： | 64/84頁 |
| 文件大小： | 531K |
| 代理商： | W77E468 |
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Preliminary W77E468
- 64 -
CLOCK CONTROL
WD1,WD0: CKCON.7, CKCON.6 - Watchdog Timer Mode select bits. These two bits select the time-
out interval for the watchdog timer. The reset time is 512 clock longer than the interrupt
time-out value.
The default Watchdog time-out is 2
17
clocks, which is the shortest time-out period. The EWT, WDIF
and RWT bits are protected by the Timed Access procedure. This prevents software from accidentally
enabling or disabling the watchdog timer. More importantly, it makes it highly improbable that errant
code can enable or disable the watchdog timer.
SERIAL PORT
Serial port in the W77E468 is a full duplex port. The W77E468 provides the user with additional
features such as the Frame Error Detection and the Automatic Address Recognition. The serial ports
are capable of synchronous as well as asynchronous communication. In Synchronous mode the
W77E468 generates the clock and operates in a half duplex mode. In the asynchronous mode, full
duplex operation is available. This means that it can simultaneously transmit and receive data. The
transmit register and the receive buffer are both addressed as SBUF Special Function Register.
However any write to SBUF will be to the transmit register, while a read from SBUF will be from the
receive buffer register. The serial port can operate in four different modes as described below.
MODE 0
This mode provides synchronous communication with external devices. In this mode serial data is
transmitted and received on the RXD line. TXD is used to transmit the shift clock. The TxD clock is
provided by the W77E468 whether the device is transmitting or receiving. This mode is therefore a
half duplex mode of serial communication. In this mode, 8 bits are transmitted or received per frame.
The LSB is transmitted/received first. The baud rate is fixed at 1/12 or 1/4 of the oscillator frequency.
This baud rate is determined by the SM2 bit (SCON.5). When this bit is set to 0, then the serial port
runs at 1/12 of the clock. When set to 1, the serial port runs at 1/4 of the clock. This additional facility
of programmable baud rate in mode 0 is the only difference between the standard 8051 and the
W77E468.
The functional block diagram is shown below. Data enters and leaves the Serial port on the RxD line.
The TxD line is used to output the shift clock. The shift clock is used to shift data into and out of the
W77E468 and the device at the other end of the line. Any instruction that causes a write to SBUF will
start the transmission. The shift clock will be activated and data will be shifted out on the RxD pin till
all 8 bits are transmitted. If SM2 = 1, then the data on RxD will appear 1 clock period before the
falling edge of shift clock on TxD. The clock on TxD then remains low for 2 clock periods, and then
goes high again. If SM2 = 0, the data on RxD will appear 3 clock periods before the falling edge of
shift clock on TxD. The clock on TxD then remains low for 6 clock periods, and then goes high again.
This ensures that at the receiving end the data on RxD line can either be clocked on the rising edge
of the shift clock on TxD or latched when the TxD clock is low.
相關(guān)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(guān)代理商/技術(shù)參數(shù) |
參數(shù)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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