欢迎访问ic37.com |
会员登录 免费注册
发布采购

PIC12C508A-04/P 参数 Datasheet PDF下载

PIC12C508A-04/P图片预览
型号: PIC12C508A-04/P
PDF下载: 下载PDF文件 查看货源
内容描述: 8引脚, 8位CMOS微控制器 [8-Pin, 8-Bit CMOS Microcontrollers]
分类和应用: 微控制器和处理器外围集成电路光电二极管PC可编程只读存储器时钟
文件页数/大小: 113 页 / 1604 K
品牌: MICROCHIP [ MICROCHIP ]
 浏览型号PIC12C508A-04/P的Datasheet PDF文件第24页浏览型号PIC12C508A-04/P的Datasheet PDF文件第25页浏览型号PIC12C508A-04/P的Datasheet PDF文件第26页浏览型号PIC12C508A-04/P的Datasheet PDF文件第27页浏览型号PIC12C508A-04/P的Datasheet PDF文件第29页浏览型号PIC12C508A-04/P的Datasheet PDF文件第30页浏览型号PIC12C508A-04/P的Datasheet PDF文件第31页浏览型号PIC12C508A-04/P的Datasheet PDF文件第32页  
PIC12C5XX  
6.2  
Prescaler  
EXAMPLE 6-1: CHANGING PRESCALER  
(TIMER0WDT)  
An 8-bit counter is available as a prescaler for the  
Timer0 module, or as a postscaler for the Watchdog  
Timer (WDT), respectively (Section 8.6). For simplicity,  
this counter is being referred to as “prescaler”  
throughout this data sheet. Note that the prescaler  
may be used by either the Timer0 module or the WDT,  
but not both. Thus, a prescaler assignment for the  
Timer0 module means that there is no prescaler for  
the WDT, and vice-versa.  
1.CLRWDT  
2.CLRF  
;Clear WDT  
;Clear TMR0 & Prescaler  
3.MOVLW '00xx1111’b ;These 3 lines (5, 6, 7)  
TMR0  
4.OPTION  
;
;
are required only if  
desired  
5.CLRWDT  
;PS<2:0> are 000 or 001  
6.MOVLW '00xx1xxx’b ;Set Postscaler to  
7.OPTION desired WDT rate  
;
To change prescaler from the WDT to the Timer0  
module, use the sequence shown in Example 6-2. This  
sequence must be used even if the WDT is disabled. A  
CLRWDT instruction should be executed before  
switching the prescaler.  
The PSA and PS2:PS0 bits (OPTION<3:0>)  
determine prescaler assignment and prescale ratio.  
When assigned to the Timer0 module, all instructions  
writing to the TMR0 register (e.g., CLRF 1,  
MOVWF 1, BSF 1,x, etc.) will clear the prescaler.  
When assigned to WDT, a CLRWDT instruction will  
clear the prescaler along with the WDT. The prescaler  
is neither readable nor writable. On a RESET, the  
prescaler contains all '0's.  
EXAMPLE 6-2: CHANGING PRESCALER  
(WDTTIMER0)  
CLRWDT  
MOVLW  
;Clear WDT and  
;prescaler  
'xxxx0xxx'  
;Select TMR0, new  
;prescale value and  
;clock source  
6.2.1  
SWITCHING PRESCALER ASSIGNMENT  
OPTION  
The prescaler assignment is fully under software control  
(i.e., it can be changed “on the fly” during program  
execution). To avoid an unintended device RESET, the  
following instruction sequence (Example 6-1) must be  
executed when changing the prescaler assignment from  
Timer0 to the WDT.  
FIGURE 6-5: BLOCK DIAGRAM OF THE TIMER0/WDT PRESCALER  
TCY ( = Fosc/4)  
Data Bus  
8
0
GP2/T0CKI  
M
U
X
1
Pin  
M
U
X
Sync  
2
Cycles  
1
TMR0 reg  
0
T0SE  
T0CS  
PSA  
0
1
8-bit Prescaler  
M
U
X
8
Watchdog  
Timer  
8 - to - 1MUX  
PS2:PS0  
PSA  
1
0
WDT Enable bit  
MUX  
PSA  
WDT  
Time-Out  
Note: T0CS, T0SE, PSA, PS2:PS0 are bits in the OPTION register.  
DS40139E-page 28  
1999 Microchip Technology Inc.  
 复制成功!