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PIC16F688-I/ST 参数 Datasheet PDF下载

PIC16F688-I/ST图片预览
型号: PIC16F688-I/ST
PDF下载: 下载PDF文件 查看货源
内容描述: 14引脚基于闪存的8位CMOS微控制器采用纳瓦技术 [14-Pin Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology]
分类和应用: 闪存微控制器
文件页数/大小: 202 页 / 3832 K
品牌: MICROCHIP [ MICROCHIP ]
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PIC16F688  
Therefore, a write to a port implies that the port pins are  
read, this value is modified and then written to the  
PORT data latch. RA3 reads ‘0’ when MCLRE = 1.  
4.0  
I/O PORTS  
There are as many as twelve general purpose I/O pins  
available. Depending on which peripherals are enabled,  
some or all of the pins may not be available as general  
purpose I/O. In general, when a peripheral is enabled,  
the associated pin may not be used as a general  
purpose I/O pin.  
The TRISA register controls the direction of the  
PORTA pins, even when they are being used as analog  
inputs. The user must ensure the bits in the TRISA  
register are maintained set when using them as analog  
inputs. I/O pins configured as analog input always read  
0’.  
4.1  
PORTA and the TRISA Registers  
Note:  
The ANSEL and CMCON0 registers must  
be initialized to configure an analog  
channel as a digital input. Pins configured  
as analog inputs will read ‘0’.  
PORTA is a 6-bit wide, bidirectional port. The  
corresponding data direction register is TRISA. Setting  
a TRISA bit (= 1) will make the corresponding PORTA  
pin an input (i.e., put the corresponding output driver in  
a High-Impedance mode). Clearing a TRISA bit (= 0)  
will make the corresponding PORTA pin an output (i.e.,  
put the contents of the output latch on the selected pin).  
The exception is RA3, which is input only and its TRISA  
bit will always read as ‘1’. Example 4-1 shows how to  
initialize PORTA.  
EXAMPLE 4-1:  
INITIALIZING PORTA  
BANKSELPORTA  
;
CLRF  
MOVLW  
MOVWF  
PORTA  
07h  
CMCON0  
;Init PORTA  
;Set RA<2:0> to  
;digital I/O  
;
BANKSELANSEL  
CLRF  
MOVLW  
MOVWF  
ANSEL  
0Ch  
TRISA  
;digital I/O  
;Set RA<3:2> as inputs  
;and set RA<5:4,1:0>  
;as outputs  
Reading the PORTA register reads the status of the  
pins, whereas writing to it will write to the PORT latch.  
All write operations are read-modify-write operations.  
REGISTER 4-1:  
PORTA: PORTA REGISTER  
U-0  
U-0  
R/W-x  
RA5  
R/W-0  
RA4  
R-x  
R/W-0  
RA2  
R/W-0  
RA1  
R/W-0  
RA0  
RA3  
bit 7  
bit 0  
Legend:  
R = Readable bit  
-n = Value at POR  
W = Writable bit  
‘1’ = Bit is set  
U = Unimplemented bit, read as ‘0’  
‘0’ = Bit is cleared  
x = Bit is unknown  
bit 7-6  
bit 5-0  
Unimplemented: Read as ‘0’  
RA<5:0>: PORTA I/O Pin bit  
1= Port pin is > VIH  
0= Port pin is < VIL  
REGISTER 4-2:  
TRISA: PORTA TRI-STATE REGISTER  
U-0  
U-0  
R/W-1  
R/W-1  
R-1  
R/W-1  
R/W-1  
R/W-1  
TRISA5  
TRISA4  
TRISA3  
TRISA2  
TRISA1  
TRISA0  
bit 7  
bit 0  
Legend:  
R = Readable bit  
-n = Value at POR  
W = Writable bit  
‘1’ = Bit is set  
U = Unimplemented bit, read as ‘0’  
‘0’ = Bit is cleared x = Bit is unknown  
bit 7-6  
bit 5-0  
Unimplemented: Read as ‘0’  
TRISA<5:0>: PORTA Tri-State Control bits  
1= PORTA pin configured as an input (tri-stated)  
0= PORTA pin configured as an output  
Note 1: TRISA<3> always reads ‘1’.  
2: TRISA<5:4> always reads ‘1’ in XT, HS and LP Oscillator modes.  
© 2007 Microchip Technology Inc.  
DS41203C-page 33  
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