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EM78P809NP 参数 Datasheet PDF下载

EM78P809NP图片预览
型号: EM78P809NP
PDF下载: 下载PDF文件 查看货源
内容描述: 8位微控制器 [8-BIT Microcontroller]
分类和应用: 微控制器
文件页数/大小: 75 页 / 532 K
品牌: ELAN [ ELAN MICROELECTRONICS CORP ]
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EM78P809N  
8-Bit Microcontroller  
In Universal Asynchronous Receiver Transmitter (UART), each transmitted or received  
character is individually synchronized by framing it with a start bit and stop bit.  
Full duplex data transfer is possible since the UART has independent transmit and  
receive sections. Double buffering for both sections allows the UART to be  
programmed for continuous data transfer.  
The figure below shows the general format of one character sent or received. The  
communication channel is normally held in the marked state (high). Character  
transmission or reception starts with a transition to the space state (low).  
The first bit transmitted or received is the start bit (low). It is followed by the data bits, in  
which the least significant bit (LSB) comes first. The data bits are followed by the parity  
bit. If present, then the stop bit or bits (high) confirm the end of the frame.  
In receiving, the UART synchronizes on the falling edge of the start bit. When two or  
three “0” are detected during three samples, it is recognized as normal start bit and the  
receiving operation is started.  
Idle state  
(mark)  
START  
bit  
Parity STOP  
D0  
D1  
D2  
Dn  
bit  
bit  
1 bit  
7 or 8 bits  
One character or frame  
1 bit  
1 bits  
Fig. 12. DATA Format in UART  
4.7.1 UART MODE:  
There are three UART modes. Mode 1 (7 bits data) and Mode 2 (8 bits data) allow the  
addition of a parity bit. The parity bit addition is not available in Mode 3. The Figure  
below shows the data format in each mode.  
1
2
3
4
5
6
7
8
9
10 11  
UMODE  
PRE  
0
7 bits DATA  
7 bits DATA  
STOP  
0
0
START  
Mode 1  
0
0
1
Parity STOP  
STOP  
START  
8 bits DATA  
8 bits DATA  
0
0
1
1
0
1
START  
START  
Mode 2  
Mode 3  
Parity STOP  
9 bits DATA  
STOP  
1
0
X
START  
Fig. 13. UART Mode  
34 •  
Product Specification (V1.0) 07.26.2005  
(This specification is subject to change without further notice)  
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