參數(shù)資料
型號: MC68HC16S2CPU20
廠商: MOTOROLA INC
元件分類: 微控制器/微處理器
英文描述: 16-BIT, 20.97 MHz, MICROCONTROLLER, PQFP100
封裝: TQFP-100
文件頁數(shù): 11/104頁
文件大?。?/td> 640K
代理商: MC68HC16S2CPU20
MOTOROLA
MC68HC16S2
14
MC68HC16S2TS/D
3.3 System Clock
The system clock in the SIM provides timing signals for the IMB modules and for an external peripheral
bus. Because the MCU is a fully static design, register and memory contents are not affected when the
clock rate changes. System hardware and software support changes in clock rate during operation.
The system clock signal can be generated in one of two ways. An internal phase-locked loop can syn-
thesize the clock from a reference frequency, or the clock signal can be input directly from an external
source. Keep these clock sources in mind while reading the rest of this section. Figure 5 is a block
diagram of the system clock.
Figure 5 System Clock Block Diagram
3.3.1 Clock Sources
The state of the MODCLK pin during reset determines the system clock source. When MODCLK is held
high during reset, the clock synthesizer generates a clock signal from a reference frequency connected
to the EXTAL pin. The clock synthesizer control register (SYNCR) determines operating frequency and
mode of operation. When MODCLK is held low during reset, the clock synthesizer is disabled and an
external system clock signal must be applied. The SYNCR control bits have no effect.
The input clock is referred to as “fref”, and can be either a crystal or an external clock source. The output
of the clock system is referred to as “fsys”. Ensure that fref and fsys are within normal operating limits.
The reference frequency for this MCU is typically 32.768 kHz, but can range from 25 kHz to 50 kHz. To
generate a reference frequency using the crystal oscillator, a reference crystal must be connected be-
tween the EXTAL and XTAL pins. Figure 6 shows a recommended circuit.
32 PLL BLOCK
PHASE
COMPARATOR
LOW-PASS
FILTER
VCO
CRYSTAL
OSCILLATOR
SYSTEM
CLOCK
SYSTEM CLOCK CONTROL
FEEDBACK DIVIDER
W
X
Y
EXTAL
XTAL
XFC
VDDSYN
CLKOUT
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MC68HC16Z1CAG16 制造商:Freescale Semiconductor 功能描述:IC16-BIT MICROCONTROLLER
MC68HC16Z1CAG20 功能描述:16位微控制器 - MCU 16 BIT MCU 1K RAM RoHS:否 制造商:Texas Instruments 核心:RISC 處理器系列:MSP430FR572x 數(shù)據(jù)總線寬度:16 bit 最大時鐘頻率:24 MHz 程序存儲器大小:8 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:2 V to 3.6 V 工作溫度范圍:- 40 C to + 85 C 封裝 / 箱體:VQFN-40 安裝風(fēng)格:SMD/SMT
MC68HC16Z1CAG20 制造商:Freescale Semiconductor 功能描述:Microcontroller