參數(shù)資料
型號： PIC16F785
廠商： Microchip Technology Inc.
英文描述： 20-Pin Flash-Based 8-Bit CMOS Microcontroller with Two-Phase Asychronous Feedback PWM, Dual High-Speed Comparators and Dual Operational Amplifiers
中文描述： 20引腳基于閃存的8兩相異步反饋的PWM，雙高位CMOS微控制器的高速比較器和雙運算放大器
文件頁數(shù)： 26/178頁
文件大?。?/td> 1620K
代理商： PIC16F785
PIC16F785
DS41249A-page 24
Preliminary
2004 Microchip Technology Inc.
3.2
Clock Source Modes
Clock source modes can be classified as external or
internal.
External clock modes rely on external circuitry for
the clock source. Examples are oscillator modules
(EC mode), quartz crystal resonators or ceramic
resonators (LP, XT, and HS modes), and
resistor-capacitor (RC mode) circuits.
Internal clock sources are contained internally
within the PIC16F785. The PIC16F785 has two
internal oscillators; the 8 MHz High-frequency
Internal Oscillator (HFINTOSC) and 31 kHz
Low-frequency Internal Oscillator (LFINTOSC).
The system clock can be selected between external or
internal clock sources via the System Clock Selection
(SCS) bit (see
Section 3.5 “Clock Switching”
).
3.3
External Clock Modes
3.3.1
OSCILLATOR START-UP TIMER (OST)
When the PIC16F785 is configured for any of the
crystal oscillator modes (LP, XT or HS), the Oscillator
Start-up Timer (OST) is enabled, which extends the
reset period to allow the oscillator additional time to
stabilize. The OST counts 1024 clock periods present
on the OSC1 pin following a Power-on Reset (POR), a
wake from Sleep, or when the Power-up Timer (PWRT)
has expired (if the PWRT is enabled). During this time,
the program counter does not increment and program
execution is suspended. The OST ensures that the
oscillator circuit, using a quartz crystal resonator or
ceramic resonator, has started and is providing a stable
system clock to the PIC16F785. Table 3-1 shows
examples where the oscillator delay is invoked.
In order to minimize latency between external oscillator
start-up and code execution, the Two-speed Clock
Start-up mode can be selected (see
Section 3.6
“Two-Speed Clock Start-up Mode”
).
TABLE 3-1:
OSCILLATOR DELAY EXAMPLES
3.3.2
EC MODE
The External Clock (EC) mode allows an externally
generated logic level as the system clock source.
When operating in this mode, an external clock source
is connected to OSC1 pin and the RA4 pin is available
for general purpose I/O. Figure 3-2 shows the pin
connections for EC mode.
The Oscillator Start-up Timer (OST) is disabled when
EC mode is selected. Therefore, there is no delay in
operation after a Power-on Reset (POR) or wake-up
from Sleep. Because the PIC16F785 design is fully
static, stopping the external clock input will have the
effect of halting the device while leaving all data intact.
Upon restarting the external clock, the device will
resume operation as if no time had elapsed.
FIGURE 3-2:
EXTERNAL CLOCK (EC)
MODE OPERATION
Switch From
Switch To
Frequency
Oscillator Delay
Comments
Sleep/POR
INTRC
INTOSC
EC, RC
EC, RC
31 kHz
125 kHz–8 MHz
DC – 20 MHz
DC – 20 MHz
5 μs–10 μs (approx.)
CPU Start-up
(1)
Following a wake-up from Sleep mode or POR,
CPU start-up is invoked to allow the CPU to
become ready for code execution.
Sleep
LFINTOSC
(31 kHz)
Sleep/POR
LP, XT, HS
31 kHz–20 MHz
1024 Clock Cycles
(OST)
1 μs (approx.)
LFINTOSC
(31 kHz)
Note
1:
INTOSC
125 kHz–8 MHz
The 5 μs–10 μs start-up delay is based on a 1 MHz System Clock.
OSC1/CLKIN
PIC16F785
I/O (OSC2)
RA4
Clock from
Ext. System
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參數(shù)描述
PIC16F785-E/ML 功能描述:8位微控制器 -MCU 3.5 KB 128 RAM 18I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風格:SMD/SMT
PIC16F785-E/P 功能描述:8位微控制器 -MCU 14KB 368 RAM 33 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風格:SMD/SMT
PIC16F785-E/SO 功能描述:8位微控制器 -MCU 3.5KB FL 128R 18 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風格:SMD/SMT
PIC16F785-E/SS 功能描述:8位微控制器 -MCU 3.5KB FL 128R 18 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風格:SMD/SMT
PIC16F785-I/ML 功能描述:8位微控制器 -MCU 3.5 KB 128 RAM 18I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風格:SMD/SMT
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