如何做SPI采用P89V51RD2 ；串行外设接口（SPI）之间的一个两RD2主奴隶

CODE FOR MASTER /* This program is to demonstrate the concept of SPI communication in which the master-slave configuration is setup by microcontroller-microcontroller interface. The code below(spi_config_master) is the configuration settings of the master. Also the the transmit protocol(spi_master_tx) is defined to send data to the slave. The connections are straight forward i.e. SS of master-->SS of slave MOSI of master-->MOSI of slave MISO of master-->MISO of slave clk from master-->clk of slave */ /* All include ../files */ #include<p89v51rd2.h> #include<LCD.h> #include<DELAY.h> #define ss_pin P1_4 //SS(chip select) pin of the masetr //function to setup the master configuration for the SPI communication void spi_config_master() { ss_pin=0; //make the SS(chip select) pin logic low because the SS pin of the slave is active low SPCR=0X50; //SPI enable bit=1; MSTR bit=1 (to configure it as master) and frequency for SPI comm. = (F)osc/4 SPSR=0X00; //disable the SPI interrupt SPDAT=0X00; //initialize the SPI data register to 0X00 } //function for the master to transmit data to slave void spi_master_tx(unsigned char data_given_to_slave) { unsigned char temp; //temporary variable to store the data to be given to slave temp=data_given_to_slave; //store the data to be passed to the slave SPDAT=temp; //pass the value in the data register of the SPI comm i.e.SPDAT while(!(SPSR&0X80)); //wait while the transmission is complete ( the SPIF bit in the SPSR register goes high when the transmission is complete) SPSR=0X00; //clear the SPIF bit } //main function void main() { //initialize the port values P0=0XFF; P1=0xFF; P3=0XFF; P2=0XFF; spi_config_master(); //setup the master configuration //infinite loop to continuously send/transmit data to slave while(1) { spi_master_tx('8'); //send the character(here the number 8 is transmitted) DELAY(5); //random delay so that the processes on the slave side are completed and hence the slave data buffer (SPDAT of slave) is not filled with the garbage values } //end of while loop } //end of main() function CODE FOR SLAVE /* This program is to demonstrate the concept of SPI communication in which the master-slave configuration is setup by microcontroller-microcontroller interface. The code below(spi_config_slave) is the configuration settings of the slave. The connections are straight forward i.e. SS of master-->SS of slave MOSI of master-->MOSI of slave MISO of master-->MISO of slave clk from master-->clk of slave */ /* All include ../files */ #include<p89v51rd2.h> #include<LCD.h> #include<DELAY.h> unsigned char data_from_master; //function to initialize the UART for communication with the PC void uart_init() { TMOD=0x20; //configure Timer/Counter1 in mode 2 (functioning as timer) for setting the correct baud rate required for communication with the PC TH1=0XFD; //setup 9600bps for the (F)osc=11.0592MHz TCON=0x40; //start timer1 by setting TR1 flag as 1 (this can also be done by writing TR=1) SCON=0X50; //set the serial IO the receive in normal mode RI=0; //receive interrupt flag is cleared TI=0; //transmit interrupt flag is cleared } //function to receive the message(character) sent from the PC unsigned char receive_data() { unsigned char received_data; //variable to store the received data received_data=SBUF; //store the received data into the variable return received_data; //return the data(variable value) to the point of call } //function to transmit the message(character) to the PC void transmit_data(unsigned char tx_data) { SBUF=tx_data; //load the data to be transmitted into the SBUF register so that it transmits while(TI==0); //wait while the data is being transmitted } //function to setup the slave configuration for the SPI communication void spi_config_slave() { SPCR=0X40; //SPI enable bit=1; MSTR bit=0 (to configure it as slave) and frequency for SPI comm. = (F)osc/4 SPSR=0X00; //disable the SPI interrupt SPDAT=0X00; //initialize the SPI data register to 0X00 } //main function void main() { //initialize the port values P1=0xFF; P3=0XFF; P2=0XFF; uart_init(); //initialize the UART configuration spi_config_slave(); //setup the master configuration //infinite loop to continuously read/receive data from master while(1) { while(!(SPSR&0X80)); //wait while the transmission is complete ( the SPIF bit in the SPSR register goes high when the transmission is complete) data_from_master=SPDAT; //store the data received/read from the master into the variable transmit_data(data_from_master); //transmit the data receive d to the UART channel to be read on the PC terminal SPSR=0X00; //clear the SPIF bit } //end of the while loop } //end of the main() function