Chapter 20, Demo 15, how to write a sector to floppy disk?

[ehenkes]

reading sectors works wonderfully. To go on to writing sectors, I tried to change the functions "read" into write functions, and it works. Important: delete FDC_CMD_EXT_SKIP, then it works!

in main(...) after successful reading of data

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	/// //////////////////////// TEST FLOPPY DRIVER
flpydsk_set_working_drive(0); // set drive 0 as current drive
flpydsk_install(6);           // floppy disk uses IRQ 6
int retVal = flpydsk_write_sector(1); // should be start of FAT1?
printformat("\nReturn Value of Write Sector: %d\n", retVal);
    /// //////////////////////// TEST FLOPPY DRIVER

flpydsk.c:

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// write a sector
void flpydsk_write_sector_imp(unsigned char head, unsigned char track, unsigned char sector)
{
	ULONG st0, cyl;
	flpydsk_dma_write(); printformat("!"); // set the DMA for write transfer

	flpydsk_send_command(FDC_CMD_WRITE_SECT | FDC_CMD_EXT_MULTITRACK |  FDC_CMD_EXT_DENSITY ); // write a sector
	flpydsk_send_command(head << 2 | _CurrentDrive ); 
	flpydsk_send_command(track);                      
	flpydsk_send_command(head);                       
	flpydsk_send_command(sector);                    
	flpydsk_send_command(FLPYDSK_SECTOR_DTL_512 );    
	flpydsk_send_command(( ( sector + 1 ) >= FLPY_SECTORS_PER_TRACK ) ? FLPY_SECTORS_PER_TRACK : sector + 1 ); 
	flpydsk_send_command(FLPYDSK_GAP3_LENGTH_3_5 );   
	flpydsk_send_command(0xFF);                       

	flpydsk_wait_irq(); 

	int j;
	for(j=0; j<7; ++j)
		flpydsk_read_data(); // read status info
	flpydsk_check_int(&st0,&cyl); // let FDC know we handled interrupt
}

// write a sector
int flpydsk_write_sector(int sectorLBA)
{
	if (_CurrentDrive >= 4) return -1;
	// convert LBA sector to CHS
	int head=0, track=0, sector=1;
	flpydsk_lba_to_chs(sectorLBA, &head, &track, &sector);
	// turn motor on and seek to track
	flpydsk_control_motor(TRUE);
	if(flpydsk_seek (track, head)) return -2;
	// write sector and turn motor off
	flpydsk_write_sector_imp(head, track, sector);
	flpydsk_control_motor(FALSE);
	return 0;
}

But it does not stop at one sector, it goes on with writing to the following sectors. How can I write exactly to the sector selected and nothing else?

Is that o.k.?
flpydsk_send_command(FDC_CMD_WRITE_SECT | FDC_CMD_EXT_MULTITRACK | FDC_CMD_EXT_DENSITY );

EDIT: yes, it is!

[ehenkes]

This is nonsense:

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flpydsk_send_command(( ( sector + 1 ) >= FLPY_SECTORS_PER_TRACK ) ? FLPY_SECTORS_PER_TRACK : sector + 1 ); 

better:

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flpydsk_send_command( 18 );

[ehenkes]

current code:

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// write a sector
void flpydsk_write_sector_imp(unsigned char head, unsigned char track, unsigned char sector)
{
	ULONG st0, cyl;
	flpydsk_dma_write(); // set the DMA for write transfer

	flpydsk_send_command( FDC_CMD_WRITE_SECT | FDC_CMD_EXT_MULTITRACK | FDC_CMD_EXT_DENSITY );  // write a sector
	flpydsk_send_command( head << 2 | _CurrentDrive );
	flpydsk_send_command( track);
	flpydsk_send_command( head);
	flpydsk_send_command( sector);
	flpydsk_send_command( FLPYDSK_SECTOR_DTL_512 );
	flpydsk_send_command( 18 );                             // full track
	flpydsk_send_command( FLPYDSK_GAP3_LENGTH_3_5 );
	flpydsk_send_command( 0xFF );

	flpydsk_wait_irq();

	// printformat("Return Values of write_sector:\n");
	int j;    
	for(j=0; j<7; ++j)
	{
		/*int val =*/ flpydsk_read_data(); // read status info: ST0 ST1 ST2 C H S Size(2: 512 Byte)
		// printformat("%d: %d  ",j,val);      		
	}
	// printformat("\n\n");
	flpydsk_check_int(&st0,&cyl); // let FDC know we handled interrupt
}

// write a sector
int flpydsk_write_sector(int sectorLBA)
{
	if (_CurrentDrive >= 4) return -1;
	// convert LBA sector to CHS
	int head=0, track=0, sector=1;
	flpydsk_lba_to_chs(sectorLBA, &head, &track, &sector);
	// turn motor on and seek to track
	flpydsk_control_motor(TRUE);
	if(flpydsk_seek (track, head)) return -2;
	// write sector and turn motor off
	flpydsk_write_sector_imp(head, track, sector);
	flpydsk_control_motor(FALSE);
	return 0;
}

[Mike]

This is nonsense: *code snip*

Hm, now that I think about it I am not sure what I was thinking when I wrote that code Going to have to fix that...

In any case, you should use FLPY_SECTORS_PER_TRACK as the parameter when calling flpydsk_send_command to avoid magic numbers.

[ehenkes]

you should use FLPY_SECTORS_PER_TRACK as the parameter

Yes, that's correct. In the beginning, I wanted to write a function

void flpydsk_write_sector_imp(unsigned char head, unsigned char track, unsigned char sector, unsigned char num_of_sectors)

It works wonderfully with num_of_sectors less than 18, if you start exact at track beginnings: sector (LBA) 0, 18, 36, 54, ..., but you get an unbelievable "echo" at this track beginnings and senseless return values, if you use "odd" sector numbers. At the time being, I do not understand this finding. Any comments? Writing to the floppy disc is important.

Here, I read and analyze the root directory:
http://www.henkessoft.de/OS_Dev/OS_Dev3 ... ocId610721
http://www.henkessoft.de/OS_Dev/Downloads/104.rar

Mike, thanks for this FDC!

More links (first is great):
// http://www.isdaman.com/alsos/hardware/fdc/floppy.htm
// http://lowlevel.brainsware.org/wiki/ind ... dress_Mark
// http://www.eit.lth.se/fileadmin/eit/cou ... iption.pdf

[ehenkes]

http://www.dynacube.net/source/index.html
There you can find the interesting module floppy.h/floppy.c
Nice educational OS from India.

[ehenkes]

With some PCs you get return values of 0 for all bits, but reads data. What can be the reason?

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printformat("Return Values of read_sector:\n");
int j;
for(j=0; j<7; ++j)
{
	int val = flpydsk_read_data(); // read status info: ST0 ST1 ST2 C H S Size(2: 512 Byte)
	printformat("%d: %d  ",j,val);
}