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PIC16F877T-20PQ 参数 Datasheet PDF下载

PIC16F877T-20PQ图片预览
型号: PIC16F877T-20PQ
PDF下载: 下载PDF文件 查看货源
内容描述: 8位微控制器\n [8-Bit Microcontroller ]
分类和应用: 微控制器
文件页数/大小: 200 页 / 3338 K
品牌: ETC [ ETC ]
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PIC16F87X  
9.2.18.3 BUS COLLISION DURING A STOP  
CONDITION  
The STOP condition begins with SDA asserted low.  
When SDA is sampled low, the SCL pin is allow to float.  
When the pin is sampled high (clock arbitration), the  
baud rate generator is loaded with SSPADD<6:0> and  
counts down to 0. After the BRG times out, SDA is  
sampled. If SDA is sampled low, a bus collision has  
occurred. This is due to another master attempting to  
drive a data '0'. If the SCL pin is sampled low before  
SDA is allowed to float high, a bus collision occurs.  
This is a case of another master attempting to drive a  
data '0' (Figure 9-25).  
Bus collision occurs during a STOP condition if:  
a) After the SDA pin has been deasserted and  
allowed to float high, SDA is sampled low after  
the BRG has timed out.  
b) After the SCL pin is deasserted, SCL is sampled  
low before SDA goes high.  
FIGURE 9-25: BUS COLLISION DURING A STOP CONDITION (CASE 1)  
SDA sampled  
low after TBRG,  
Set BCLIF  
TBRG  
TBRG  
TBRG  
SDA  
SDA asserted low  
SCL  
PEN  
BCLIF  
P
'0'  
'0'  
'0'  
'0'  
SSPIF  
FIGURE 9-26: BUS COLLISION DURING A STOP CONDITION (CASE 2)  
TBRG  
TBRG  
TBRG  
SDA  
SCL goes low before SDA goes high  
Set BCLIF  
Assert SDA  
SCL  
PEN  
BCLIF  
P
'0'  
'0'  
SSPIF  
DS30292B-page 92  
1999 Microchip Technology Inc.  
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