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CP82C55A-5 参数 Datasheet PDF下载

CP82C55A-5图片预览
型号: CP82C55A-5
PDF下载: 下载PDF文件 查看货源
内容描述: CMOS可编程外设接口 [CMOS Programmable Peripheral Interface]
分类和应用:
文件页数/大小: 26 页 / 236 K
品牌: INTERSIL [ Intersil ]
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82C55A  
Functional Description  
I/O  
PA7-  
PA0  
+5V  
GND  
GROUP A  
PORT A  
(8)  
POWER  
SUPPLIES  
Data Bus Buffer  
GROUP A  
CONTROL  
This three-state bi-directional 8-bit buffer is used to interface  
the 82C55A to the system data bus. Data is transmitted or  
received by the buffer upon execution of input or output  
instructions by the CPU. Control words and status informa-  
tion are also transferred through the data bus buffer.  
I/O  
PC7-  
PC4  
GROUP A  
PORT C  
UPPER  
(4)  
BI-DIRECTIONAL  
DATA BUS  
I/O  
DATA  
PC3-  
PC0  
BUS  
BUFFER  
GROUP B  
PORT C  
LOWER  
(4)  
D7-D0  
8-BIT  
INTERNAL  
DATA BUS  
Read/Write and Control Logic  
The function of this block is to manage all of the internal and  
external transfers of both Data and Control or Status words.  
It accepts inputs from the CPU Address and Control busses  
and in turn, issues commands to both of the Control Groups.  
I/O  
PB7-  
PB0  
RD  
WR  
A1  
READ  
WRITE  
CONTROL  
LOGIC  
GROUP B  
CONTROL  
GROUP B  
PORT B  
(8)  
A0  
RESET  
(CS) Chip Select. A “low” on this input pin enables the  
communcation between the 82C55A and the CPU.  
CS  
(RD) Read. A “low” on this input pin enables 82C55A to send  
the data or status information to the CPU on the data bus. In  
essence, it allows the CPU to “read from” the 82C55A.  
FIGURE 1. 82C55A BLOCK DIAGRAM. DATA BUS BUFFER,  
READ/WRITE, GROUP A & B CONTROL LOGIC  
FUNCTIONS  
(WR) Write. A “low” on this input pin enables the CPU to  
write data or control words into the 82C55A.  
(RESET) Reset. A “high” on this input initializes the control  
register to 9Bh and all ports (A, B, C) are set to the input  
mode. “Bus hold” devices internal to the 82C55A will hold  
the I/O port inputs to a logic “1” state with a maximum hold  
current of 400µA.  
(A0 and A1) Port Select 0 and Port Select 1. These input  
signals, in conjunction with the RD and WR inputs, control  
the selection of one of the three ports or the control word  
register. They are normally connected to the least significant  
bits of the address bus (A0 and A1).  
Group A and Group B Controls  
82C55A BASIC OPERATION  
The functional configuration of each port is programmed by  
the systems software. In essence, the CPU “outputs” a con-  
trol word to the 82C55A. The control word contains  
information such as “mode”, “bit set”, “bit reset”, etc., that ini-  
tializes the functional configuration of the 82C55A.  
INPUT OPERATION  
A1  
0
A0  
0
RD WR CS  
(READ)  
Port A Data Bus  
Port B Data Bus  
Port C Data Bus  
Control Word Data Bus  
0
0
0
0
1
1
1
1
0
0
0
0
Each of the Control blocks (Group A and Group B) accepts  
“commands” from the Read/Write Control logic, receives  
“control words” from the internal data bus and issues the  
proper commands to its associated ports.  
0
1
1
0
Control Group A - Port A and Port C upper (C7 - C4)  
Control Group B - Port B and Port C lower (C3 - C0)  
1
1
OUTPUT OPERATION  
(WRITE)  
The control word register can be both written and read as  
shown in the “Basic Operation” table. Figure 4 shows the  
control word format for both Read and Write operations.  
When the control word is read, bit D7 will always be a logic  
“1”, as this implies control word mode information.  
0
0
1
1
0
1
0
1
1
1
1
1
0
0
0
0
0
0
0
0
Data Bus Port A  
Data Bus Port B  
Data Bus Port C  
Data Bus Control  
DISABLE FUNCTION  
Data Bus Three-State  
Data Bus Three-State  
X
X
X
X
X
1
X
1
1
0
3