参数资料
型号: PIC16F688-E/ML
厂商: Microchip Technology
文件页数: 130/204页
文件大小: 0K
描述: IC PIC MCU FLASH 4KX14 16QFN
产品培训模块: Asynchronous Stimulus
标准包装: 91
系列: PIC® 16F
核心处理器: PIC
芯体尺寸: 8-位
速度: 20MHz
连通性: UART/USART
外围设备: 欠压检测/复位,POR,WDT
输入/输出数: 12
程序存储器容量: 7KB(4K x 14)
程序存储器类型: 闪存
EEPROM 大小: 256 x 8
RAM 容量: 256 x 8
电压 - 电源 (Vcc/Vdd): 2 V ~ 5.5 V
数据转换器: A/D 8x10b
振荡器型: 内部
工作温度: -40°C ~ 125°C
封装/外壳: 16-VQFN 裸露焊盘
包装: 管件
配用: AC164324-ND - MODULE SKT FOR MPLAB 8DFN/16QFN
XLT16QFN1-ND - SOCKET TRANSITION 14DIP TO 16QFN
AC162061-ND - HEADER INTRFC MPLAB ICD2 20PIN
AC162056-ND - HEADER INTERFACE ICD2 16F688
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2009 Microchip Technology Inc.
DS41203E-page 29
PIC16F688
3.6
Clock Switching
The system clock source can be switched between
external and internal clock sources via software using
the System Clock Select (SCS) bit of the OSCCON
register.
3.6.1
SYSTEM CLOCK SELECT (SCS) BIT
The System Clock Select (SCS) bit of the OSCCON
register selects the system clock source that is used for
the CPU and peripherals.
When the SCS bit of the OSCCON register = 0,
the system clock source is determined by
configuration of the FOSC<2:0> bits in the
Configuration Word register (CONFIG).
When the SCS bit of the OSCCON register = 1,
the system clock source is chosen by the internal
oscillator frequency selected by the IRCF<2:0>
bits of the OSCCON register. After a Reset, the
SCS bit of the OSCCON register is always
cleared.
3.6.2
OSCILLATOR START-UP TIME-OUT
STATUS (OSTS) BIT
The Oscillator Start-up Time-out Status (OSTS) bit of
the OSCCON register indicates whether the system
clock is running from the external clock source, as
defined by the FOSC<2:0> bits in the Configuration
Word register (CONFIG), or from the internal clock
source. In particular, OSTS indicates that the Oscillator
Start-up Timer (OST) has timed out for LP, XT or HS
modes.
3.7
Two-Speed Clock Start-up Mode
Two-Speed Start-up mode provides additional power
savings by minimizing the latency between external
oscillator start-up and code execution. In applications
that make heavy use of the Sleep mode, Two-Speed
Start-up will remove the external oscillator start-up
time from the time spent awake and can reduce the
overall power consumption of the device.
This mode allows the application to wake-up from
Sleep, perform a few instructions using the INTOSC
as the clock source and go back to Sleep without
waiting for the primary oscillator to become stable.
When the oscillator module is configured for LP, XT or
HS modes, the Oscillator Start-up Timer (OST) is
(OST)”). The OST will suspend program execution until
1024 oscillations are counted. Two-Speed Start-up
mode minimizes the delay in code execution by
operating from the internal oscillator as the OST is
counting. When the OST count reaches 1024 and the
OSTS bit of the OSCCON register is set, program
execution switches to the external oscillator.
3.7.1
TWO-SPEED START-UP MODE
CONFIGURATION
Two-Speed Start-up mode is configured by the
following settings:
IESO (of the Configuration Word register) = 1;
Internal/External Switchover bit (Two-Speed Start-
up mode enabled).
SCS (of the OSCCON register) = 0.
FOSC<2:0> bits in the Configuration Word
register (CONFIG) configured for LP, XT or HS
mode.
Two-Speed Start-up mode is entered after:
Power-on Reset (POR) and, if enabled, after
Power-up Timer (PWRT) has expired, or
Wake-up from Sleep.
If the external clock oscillator is configured to be
anything other than LP, XT or HS mode, then Two-
Speed Start-up is disabled. This is because the external
clock oscillator does not require any stabilization time
after POR or an exit from Sleep.
3.7.2
TWO-SPEED START-UP
SEQUENCE
1.
Wake-up from Power-on Reset or Sleep.
2.
Instructions begin execution by the internal
oscillator at the frequency set in the IRCF<2:0>
bits of the OSCCON register.
3.
OST enabled to count 1024 clock cycles.
4.
OST timed out, wait for falling edge of the
internal oscillator.
5.
OSTS is set.
6.
System clock held low until the next falling edge
of new clock (LP, XT or HS mode).
7.
System clock is switched to external clock
source.
Note:
Any automatic clock switch, which may
occur from Two-Speed Start-up or Fail-Safe
Clock Monitor, does not update the SCS bit
of the OSCCON register. The user can
monitor the OSTS bit of the OSCCON
register to determine the current system
clock source.
Note:
Executing a SLEEP instruction will abort
the oscillator start-up time and will cause
the OSTS bit of the OSCCON register to
remain clear.
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