1. In SPI, I have read simultaneous data is send out & send in.
My question is since processor can handle only one task at a time. How can it work on two registers simulatneoulsy.

2. I successfully send data from master & slave can read it. but when I have to send data back to master, I am not able tyo send byte. Its just garbage value or mostly 0.

Master Code:

void main(void)
{
unsigned char read_byte, i=0;

spi_setting();
ss =0; //enable the slave

while(1)
{
SSPBUF = i++; // write data
while(BF == 0); //wait till complete
read_byte = SSPBUF; // not getting write byte from slave
}


}


void spi_setting(void)
{
ss=1; //set SS pin high, as initial slave module will be
ssio=0;

sckio =0; //setting clock as o/p, data out as outpot &
sdiio =1;
sdoio =0;

SSPSTAT = 0x40; // data is sampled in middle of o/p
SSPCON = 0x31; //spi master mode, fosc/16

}




Slave Code:

void main(void)
{
unsigned char read_byte;

spi_setting();

while(1)
{
while(BF==0);
read_byte = SSPBUF;
SSPBUF = 0x90; // not able to send this byte

}


}


void spi_setting(void)
{

ADCON1 = 0x06;
ssio = 1; // make slave select as input

sckio = 1; //make clock input, data in as input & data out as
sdiio = 1;
sdoio = 0;

SSPSTAT = 0x40; // data is sampled in middle of o/p
SSPCON = 0x34; //spi alve mode mode, fosc/16

}

 

any help

 

The SPI is impemented in hardware. Think of it as a pipe with an inlet and an outlet, or a room with an IN-door and an OUT-door. Data goes in one door and out the other. This is done by the hardware and all the MCU has to do is read the contents of the room.

 

thanks for that
any comments/help in source code??????