欢迎访问ic37.com |
会员登录 免费注册
发布采购

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 ]
 浏览型号PIC16F688-I/ST的Datasheet PDF文件第32页浏览型号PIC16F688-I/ST的Datasheet PDF文件第33页浏览型号PIC16F688-I/ST的Datasheet PDF文件第34页浏览型号PIC16F688-I/ST的Datasheet PDF文件第35页浏览型号PIC16F688-I/ST的Datasheet PDF文件第37页浏览型号PIC16F688-I/ST的Datasheet PDF文件第38页浏览型号PIC16F688-I/ST的Datasheet PDF文件第39页浏览型号PIC16F688-I/ST的Datasheet PDF文件第40页  
PIC16F688  
4.2.3  
INTERRUPT-ON-CHANGE  
4.2  
Additional Pin Functions  
Each of the PORTA pins is individually configurable as  
an interrupt-on-change pin. Control bits IOCAx enable  
or disable the interrupt function for each pin. Refer to  
Register 4-5. The interrupt-on-change is disabled on a  
Power-on Reset.  
Every PORTA pin on the PIC16F688 has an interrupt-  
on-change option and a weak pull-up option. PORTA  
also provides an Ultra Low-Power Wake-up option. The  
next three sections describe these functions.  
4.2.1  
ANSEL REGISTER  
For enabled interrupt-on-change pins, the values are  
compared with the old value latched on the last read of  
PORTA. The ‘mismatch’ outputs of the last read are  
OR’d together to set the PORTA Change Interrupt Flag  
bit (RAIF) in the INTCON register.  
The ANSEL register is used to configure the Input  
mode of an I/O pin to analog. Refer to Register 4-3.  
Setting the appropriate ANSEL bit high will cause all  
digital reads on the pin to be read as ‘0’ and allow  
analog functions on the pin to operate correctly.  
This interrupt can wake the device from Sleep. The user,  
in the Interrupt Service Routine, clears the interrupt by:  
The state of the ANSEL bits has no affect on digital  
output functions. A pin with TRIS clear and ANSEL set  
will still operate as a digital output, but the Input mode  
will be analog. This can cause unexpected behavior  
when executing read-modify-write instructions on the  
affected port.  
a) Any read or write of PORTA. This will end the  
mismatch condition, then  
b) Clear the flag bit RAIF.  
A mismatch condition will continue to set flag bit RAIF.  
Reading PORTA will end the mismatch condition and  
allow flag bit RAIF to be cleared. The latch holding the  
last read value is not affected by a MCLR nor BOR  
Reset. After these Resets, the RAIF flag will continue  
to be set if a mismatch is present.  
4.2.2  
WEAK PULL-UPS  
Each of the PORTA pins, except RA3, has an  
individually configurable internal weak pull-up. Control  
bits WPUAx enable or disable each pull-up. Refer to  
Register 4-4. Each weak pull-up is automatically turned  
off when the port pin is configured as an output. The  
pull-ups are disabled on a Power-on Reset by the  
RAPU bit of the OPTION register. A weak pull-up is  
automatically enabled for RA3 when configured as  
MCLR and disabled when RA3 is an I/O. There is no  
software control of the MCLR pull-up.  
Note:  
If a change on the I/O pin should occur  
when the read operation is being executed  
(start of the Q2 cycle), then the RAIF  
interrupt flag may not get set.  
REGISTER 4-3:  
ANSEL: ANALOG SELECT REGISTER  
R/W-1  
ANS7  
R/W-1  
ANS6  
R/W-1  
ANS5  
R/W-1  
ANS4  
R/W-1  
ANS3  
R/W-1  
ANS2  
R/W-1  
ANS1  
R/W-1  
ANS0  
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 7-0  
ANS<7:0>: Analog Select bits  
Analog select between analog or digital function on pins AN<7:0>, respectively.  
1= Analog input. Pin is assigned as analog input(1)  
0= Digital I/O. Pin is assigned to port or special function.  
.
Note 1: Setting a pin to an analog input automatically disables the digital input circuitry, weak pull-ups and  
interrupt-on-change, if available. The corresponding TRIS bit must be set to Input mode in order to allow  
external control of the voltage on the pin.  
DS41203C-page 34  
© 2007 Microchip Technology Inc.  
 复制成功!