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ual entry address to go . MCS-51 microcontroller system memory Features

MCU memory structure has two important features: First, the data memory and program memory completely separate, two is a memory inside and outside of the points. Overall, the chip and off-chip memory, extended memory constitutes the entire microcomputer application system memory system .

There is also a single chip is an important parallel I / O port circuitry. MCS-51 has four 8-bit parallel bidirectional I / O ports , denoted as P0, P1, P2, P3, in fact, they have been included in the list of special registers . In addition to these four ports are byte-addressable , you can also press -bit addressing , four ports combined total of 32 .

In SCM , the mouth is a collection of data input buffer , the data output drivers and latch and many other features in one of the I / O circuits . The MCS-51 four port structure of the circuit is basically the same, but they are also different characteristics , so the function and use of a certain difference between the mouth . In learning to master each port must use .

MCS-51 microcontroller clock circuit and timing

MCU clock circuit for generating a clock signal needed for the work , the microcontroller itself is a complex synchronous sequential circuit , in order to ensure the realization of synchronous operation mode , the circuit should be under the control of the clock signal only strictly chronological work . The timing of the study is the instruction execution between the respective signals in the time .

To understand the generation and function of the clock circuit , is joined to the external crystal oscillator frequency is calculated timing of the timing unit .

Digital filter (digital filter) is a digital multiplier , an adder and a delay element consisting of a device. Its function is an input to the discrete signal processing for computing a digital code in order to change the purpose of the signal spectrum . As computer technology and the development of large scale integrated circuit , a digital filter is already available computer software can also be used to achieve large-scale integrated real-time digital hardware . The digital filter is a discrete -time system ( according to a predetermined algorithm , the input discrete-time signal is converted to the discrete-time signal output required a lot of functional device ) . Application of digital filter processing analog signals, the input must first be bandlimited analog signal , sampling and analog-digital conversion. Digital filter input signal sample rate should be greater than twice the signal bandwidth to be processed , the frequency response having the sampling cycle is repeated at intervals of frequency characteristics, and to collapse the frequency is 1/ 2 the sampling frequency in a mirror symmetry. In order to obtain an analog signal , the digital filter processing of the output digital signal is subject to digital to analog conversion , smooth. Digital filter with high accuracy, high reliability, can be programmed to change behavior or reuse, ease of integration and so on. Digital filter in speech signal processing, image signal processing, medical bio- signal processing and other applications have been widely used. Digital filter with a low pass, high pass, band pass , band stop and all-pass and other types. It can be time-invariant or time- varying, causal