c problem

[david]

i dont do c but need help in understanding what this bit of code does.
i am only interested in the sendmmc() function.
does it send the command Command(0x51,0,512,0xFF) then send 512 * ff
on spi bus
or send the comand 512 times ?


David






bit sendmmc() // send 512 bytes from the MMC via the serial port
{
uns16 i;
// 512 byte-read-mode
if (Command(0x51,0,512,0xFF) !=0) {
SerString("MMC: read error 1 ");
return 1;
}
while(SPI(0xFF) != 0xFE); // wait for 0xFE -
start of any transmission
for(i=0;
i < 512; i++)
{
while(!TXIF); // wait until TXREG is
empty
TXREG = SPI(0xFF); // get MMC byte and send
via RS232
}
serialterminate();
SPI(0xFF); // at the end, send 2 dummy bytes
SPI(0xFF);
return 0;
}

void main(void)
{
InitUSART(); // initialize serial port
initint(); // initialize interrupts

ADCON1=0x6; // PortA Digital
// set ports for I/O
TRISC = 0b.1101.0011; // sck rc3-0, sdo rc5-0, CS rc2-0.
TRISB = 0b.0000.0010; // RB2>TX, RB1>RX

SerString("PIC online "); // start message
// SerString(0x00); // start message

// init MMC and send message if ok
if (MMC_Init()) SerString("MMC online ");

fillram(); // fill the RAM with ASCII characters
writeramtommc(); // write RAM to MMC
sendmmc(); // send 512 bytes of the MMC via serial port

while(1) {
nop();
nop();
}
}

 

[James Beck]

i dont do c but need help in understanding what this bit of code does.
i am only interested in the sendmmc() function.
does it send the command Command(0x51,0,512,0xFF) then send 512 * ff
on spi bus
or send the comand 512 times ?


David






bit sendmmc() // send 512 bytes from the MMC via the serial port
{
uns16 i;
// 512 byte-read-mode
if (Command(0x51,0,512,0xFF) !=0) {
SerString("MMC: read error 1 ");
return 1;
}

It sends the command, looks at the return code, and reports the error if
it occurred. It appears that the command is sent once, but that is no
guarantee that the function Command(..) does not try more than once
before returning an error.

while(SPI(0xFF) != 0xFE); // wait for 0xFE -
start of any transmission
for(i=0;
i < 512; i++)
{
while(!TXIF); // wait until TXREG is
empty
TXREG = SPI(0xFF); // get MMC byte and send
via RS232
}

It looks like it then sends 512 bytes from the SPI to the serial port.

serialterminate();
SPI(0xFF); // at the end, send 2 dummy bytes
SPI(0xFF);

It looks like the SPI peripheral needs two dummy bytes to finish the
transmission and be set for the next command.

That is my best guess without seeing the rest of the code.