Floppy Disk Controller Confusion

[Nessphoro]

Hey guys,

So I've been reading Floppy Disk Controller tutorial, and this part is unclear to me.

Send a Version command to the controller.
Verify that the result byte is 0x90 -- if it is not, it might be a good idea to abort and not support the floppy subsystem. Almost all of the code based on this article will work, even on the oldest chipsets -- but there are a few commands that will not.
If you don't want to bother having to send another Configure command after every Reset procedure, then:
Send a better Configure command to the controller. A suggestion would be: drive polling mode off, FIFO on, threshold = 8, implied seek on, precompensation 0.
send a Lock command.
Do a Controller Reset procedure.
Send a Recalibrate command to each of the drives.

Send a Version command to the controller??? What port?
Verify the result byte is 0x90??? What port?

Thats what I'm wondering about,

Thanks

[bluemoon]

Send a Version command to the controller??? What port?
Verify the result byte is 0x90??? What port?

All commands, parameter information, result codes, and disk data transfers go through the FIFO port.

It's noted on the same tutorial page

So I've been reading Floppy Disk Controller tutorial

No, you don't.

[Nessphoro]

Okay, then why when I do this
(DATA_FIFO and else are taken from the article)

Code: Select all

outb(DATA_FIFO,VERSION);
unsigned char result= inb(DATA_FIFO);

I always get 0?
(Using QEMU)

[Nessphoro]

Problem solved

[Brendan]

Hi,

Okay, then why when I do this
(DATA_FIFO and else are taken from the article)

Code: Select all

outb(DATA_FIFO,VERSION);
unsigned char result= inb(DATA_FIFO);

I always get 0?
(Using QEMU)

You need to start by writing some small, very low level routines to access various registers correctly. For most things, you can't just read/write the registers, but have to poll certain status flags until the device is ready before reading/writing, and have a time-out in case something is wrong.

For example, to send any command byte you have to poll the MSR register in a loop (with a time-out in case something is wrong) until the RQM flag is 1 and the DIO flag is 0, and only when these flags are right can you send your command byte to the FIFO register. Write a "int send_command_byte(unsigned char byte)" function to do this for you (that returns an "TIMEOUT" error if something is wrong).

For another example, before reading a result byte you have to poll the MSR register in a loop (with a time-out in case something is wrong) until the RQM flag is 1 and the DIO flag is 1, and only then can you read the result byte from the FIFO register. Write a "int get_result_byte(unsigned char *outByte)" function to do this for you (that returns an "TIMEOUT" error if something is wrong).

Then you'd do something like:

Code: Select all

    status = send_command_byte(COMMAND_VERSION);
    if(status == OK) {
        status = get_result_byte(&version);
    }
    if(status != OK) {
        /* Handle time-out error - maybe reset the controller and retry, and if it fails
         * a second time give up (assume device is faulty)
         */
    }

Cheers,

Brendan