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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 ]
 浏览型号PIC16F877T-20PQ的Datasheet PDF文件第87页浏览型号PIC16F877T-20PQ的Datasheet PDF文件第88页浏览型号PIC16F877T-20PQ的Datasheet PDF文件第89页浏览型号PIC16F877T-20PQ的Datasheet PDF文件第90页浏览型号PIC16F877T-20PQ的Datasheet PDF文件第92页浏览型号PIC16F877T-20PQ的Datasheet PDF文件第93页浏览型号PIC16F877T-20PQ的Datasheet PDF文件第94页浏览型号PIC16F877T-20PQ的Datasheet PDF文件第95页  
PIC16F87X  
9.2.18.2 BUS COLLISION DURING A REPEATED  
START CONDITION  
sampled high, the BRG is reloaded and begins count-  
ing. If SDA goes from high to low before the BRG times  
out, no bus collision occurs, because no two masters  
can assert SDA at exactly the same time.  
During a Repeated Start condition, a bus collision  
occurs if:  
If, however, SCL goes from high to low before the BRG  
times out and SDA has not already been asserted, a  
bus collision occurs. In this case, another master is  
attempting to transmit a data ’1’ during the Repeated  
Start condition.  
a) A low level is sampled on SDA when SCL goes  
from low level to high level.  
b) SCL goes low before SDA is asserted low, indi-  
cating that another master is attempting to trans-  
mit a data ’1’.  
If at the end of the BRG time out both SCL and SDA are  
still high, the SDA pin is driven low, the BRG is reloaded  
and begins counting. At the end of the count, regard-  
less of the status of the SCL pin, the SCL pin is driven  
low and the Repeated Start condition is complete  
(Figure 9-23).  
When the user deasserts SDA and the pin is allowed to  
float high, the BRG is loaded with SSPADD<6:0> and  
counts down to 0. The SCL pin is then deasserted, and  
when sampled high, the SDA pin is sampled. If SDA is  
low, a bus collision has occurred (i.e. another master is  
attempting to transmit a data ’0’). If however SDA is  
FIGURE 9-23: BUS COLLISION DURING A REPEATED START CONDITION (CASE 1)  
SDA  
SCL  
Sample SDA when SCL goes high.  
If SDA = 0, set BCLIF and release SDA and SCL  
RSEN  
BCLIF  
Cleared in software  
'0'  
'0'  
'0'  
S
'0'  
SSPIF  
FIGURE 9-24: BUS COLLISION DURING REPEATED START CONDITION (CASE 2)  
TBRG  
TBRG  
SDA  
SCL  
SCL goes low before SDA,  
Set BCLIF. Release SDA and SCL  
BCLIF  
RSEN  
Interrupt cleared  
in software  
'0'  
'0'  
'0'  
'0'  
S
SSPIF  
1999 Microchip Technology Inc.  
DS30292B-page 91  
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