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MPC82L54AS2 参数 Datasheet PDF下载

MPC82L54AS2图片预览
型号: MPC82L54AS2
PDF下载: 下载PDF文件 查看货源
内容描述: 8位微控制器 [8-bit micro-controller]
分类和应用: 微控制器
文件页数/大小: 74 页 / 1587 K
品牌: MEGAWIN [ MEGAWIN TECHNOLOGY CO., LTD ]
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SFR: P3M1 (P3 Configuration 1)  
Bit-7  
Bit-6  
Bit-5  
Bit-4  
Bit-3  
Bit-2  
Bit-1  
Bit-0  
P3M17  
P3M16  
P3M15  
P3M14  
P3M13  
P3M12  
P3M11  
P3M10  
Configuration of I/O port  
PxM0n  
PxM1n  
Port Mode  
0
0
1
0
1
Quasi-bidirectional (default)  
Push-Pull output  
0
1
Input Only (High-impedance)  
Open-Drain Output  
1
(x = 0, 1, 2 or 3  
n = 7, 6, 5, 4, 3, 2, 1 or 0)  
Quasi-bidirectional Mode  
Port pins in quasi-bidirectional output mode function similar to the standard 8051 port pins. A  
quasi-bidirectional port can be used as an input and output without the need to reconfigure the  
port. This is possible because when the port outputs a logic high, it is weakly driven, allowing  
an external device to pull the pin low. When the pin outputs low, it is driven strongly and able  
to sink a large current. There are three pull-up transistors in the quasi-bidirectional output that  
serve different purposes.  
One of these pull-ups, called the “very weak” pull-up, is turned on whenever the port register  
for the pin contains a logic “1”. This very weak pull-up sources a very small current that will  
pull the pin high if it is left floating.  
A second pull-up, called the “weak” pull-up, is turned on when the port register for the pin  
contains a logic “1” and the pin itself is also at a logic “1” level. This pull-up provides the  
primary source current for a quasi-bidirectional pin that is outputting a ‘1’. If this pin is pulled  
low by the external device, this weak pull-up turns off, and only the very weak pull-up remains  
on. In order to pull the pin low under these conditions, the external device has to sink enough  
current to over-power the weak pull-up and pull the port pin below its input threshold voltage.  
The third pull-up is referred to as the “strong” pull-up. This pull-up is used to speed up  
low-to-high transitions on a quasi-bidirectional port pin when the port register changes from a  
logic “0” to a logic “1”. When this occurs, the strong pull-up turns on for two CPU clocks,  
quickly pulling the port pin high.  
MEGAWIN  
MPC82x54A Data Sheet  
21  
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