How to access R0 to R7 registers in Keil C?

you can use the following Program to access R0 to R7 registers in Keil C


{

unsigned char R0Val;

_asm

MOV A, R0
MOV _R0Val, A

_endasm

}

OR

{

unsigned char R0Val;

#pragma ASM

MOV A, R0
MOV _R0Val, A

#pragma ENDASM

}

C variables have to be prefixed by '_' or underscore character, to be accessible in the assembly section of the C code.

Hope this helps.

Program for multiplexing of led displays for pic microcontrollers

Suppose you want to design the ac digital voltmeter rang up to 0-300v or above, by using any pic 8-bit mcu, and want to use 3, 7-segment display for it then there can be a problem as to how do you indicate such large value on display

then you can go with the following approch

use BCD to 7 segment converter, so that only 4 bits can be used to control a single 7 seven segment display..... so in total u need 12 output lines. you can get 12 output bits by using 2 different ports of any suitable 8 bit microcontroller. link to one such converter http://www.ee.washington.edu/stores/DataSheets/74ls/74ls47.pdf

use 7 bits from one port for all 3 displays and use 3 other bits to select led's this is done very fast so human eye can not make out that the displays are glowing sequencially and not continously.
here is sample code for pic

#include
#include

void DisplayNumber( unsigned int number );

void main()
{
trisb = 0;
trisa = 0xFF;

unsigned int randNumb = 0;

while( 1 )
{

while( porta.0 == 0 ) // wait for key pressed
DisplayNumber( randNumb ); // display number to keep display refreshed

// while key pressed increment counter
// Number will be random based on how long input is turned on
while( porta.0 == 1 )
{
randNumb++;
if( ++randNumb > 9999 )
randNumb = 0;
}

// display a series of random numbers so it looks like we are
char j;
for( j = 0; j < x =" rand();" i =" 0;" i =" 0x01;" i =" 0b1000;">>= 1 )
{
digit = number % 10;
number /= 10;

portb = digit & 0x0F;
portb = (digit & 0x0F) | (i <<>

Assembly program for a real time clock

Following is the Assembly language program for a real time clock

Code:

LCALL 061D
AGAIN MOV DPTR, #2845
REPEAT DEC82 ; Decrement DPL
MOVX A,@DPTR
MOV R3,A
MOV R5,#02
LCALL 059E
MOV A,20
LCALL 2006
MOVA,82
CJNE A,#42; REPEAT (ED)
MOVA,#OD ; OD = ASCII FOR ENTER
LCALL 2006
LJMP; AGAIN ( 6003 )

To change the RTC

2844-hrs
2843-minutes
2842-seconds

Interfacing Multimedia card with ATMega 128

I am interfacing Multimedia card with ATMega 128 through SPI protocol. For that while reading data from Multimedia Card, I use to send dummy bytes through MOSI and receive data through MISO in SPDR.
hears some routine. Take a Look on them

void SPI_init(void)

{

DDRB |= (1 << SPICS); // 0 set port B SPI chip select to output

DDRB |= (1 << SPICLK); // 1 set port B SPI clock to output

DDRB |= (1 << SPIDO); // 2 set port B SPI data out to output

DDRB &= ~(1 << SPIDI); // 3 set port B SPI data input to input

SPCR = (1 << SPE) | (1 << MSTR); //pg#168(391)

SPICS_ON();

}





char Command(char befF, int AdrH, int AdrL, char CRC )

{ // sends a command to the MMC

SPI(0xFF);

SPI(befF);

SPI((AdrH >> 8));

SPI(AdrH);

SPI((AdrL >> 8));

SPI(AdrL);

SPI(CRC);

SPI(0xFF);

return SPI(0xFF); // return the last received character

}



unsigned char SPI(unsigned char mydata)//transmit through SPI data out
line(MOSI)

{

//unsigned char Rx_SPDR=0xDC, Rx;

SPDR = mydata; //1 Byte data

while(!(SPSR & (1<<SPIF))) // wait for complete transmission

;

//printf("\r\nRx_SPDR = 0x%X", Rx_SPDR);

//Rx=SPDR;

//printf("\r\nRx_SPDR = 0x%X", Rx_SPDR);

return SPDR; //return the received value of SPDR

}





int Read_from_MMC(void) { // send 512 bytes from the MMC via the serial port

int i;

// 512 byte-read-mode

if (Command(0x51,0,512,0xFF) != 0)

{

printf("MMC: read error 1 ");

return 0;

}

// wait for 0xFE - start of any transmission

// ATT: typecast (char)0xFE is a must!

while(SPI(0xFF) != (char)0xFE);



for(i=0; i < 512; i++)

{

while(!(UCSR0A & (1 << UDRE0))); // wait for serial port

/*Here we are transmitting 0xFF through MOSI and then assigning the received
character to USART Data Register*/

UDR0 = SPI(0xFF); // send character

}





// at the end, send 2 dummy bytes

SPI(0xFF); // actually this returns the CRC/checksum byte

SPI(0xFF);

return 1;

}

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A C program for serial communation with pc using 8051

This program will read a complete line coming through my COM port in 8051.


This is the subroutine or function in c for accept line from serial port
void get_line(void)
{
char c, index=0;

while(c = getchar() != '\n')
{
buffer[index++] = c;
}
}


The main program
void main()
{
PCON = 0x80; // Double Baud Rate
SCON = 0x50; // SCON: mode 1, 8-bit UART, enable rcvr
TMOD |= 0x20; // TMOD: timer 1, mode 2, 8-bit reload
TH1 = BAUD_CONST; // TH1: reload value for desired baud. Calculate this for your crystal frequency
TR1 = 1; // TR1: timer 1 run
TI = 1;
RI = 0;

get_line(); //function call

}

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TCP/IP on PIC 18 series

TCP/IP stack is readly avalibe from Microchip.com
implement the tcp/ip or udp port in your projects using ENC28j60 from microchip, using SPI port

or try this

Go to www.microchip.com and search for

PIC18F97J60

It comes with ready TCP IP stack and it will help you...let me know if you need further information...

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