questions to di and did debugger commands
 

1. what triggers this break?
2. what are the numbers and letters stand for?
DSKLEN: drive 0 motor on cylinder 0 sel yes rw mfmpos 52533/101344
5295 5555 5255 5555|5495 5555 5555 5555 5495 5555 5555 5555 5295 5555 5255 5555 5295
side 0 dma 2 off 1 word 5555 pt 00002064 len 9CBE bytr 80AA adk 1100 sync 0000

3. also with
4. are there different log level and for what?
did <log level> Enable disk logging.

5. for what is this breakpoint and logging feature helpful? maybe to understand mfm/gcr-encoding?
or disc data structure?

DMA start when track is zero. (R=read default, W=write, P=DSKBYTR CPU read)

Floppy drive state (motor, cylinder, selected, side select) and register contents (DMA pointer, length, DSKBYTR, ADKCON, DSKSYNC)

MFMPOS = current bit position of track/total length. Raw bit stream dump (| = current position)

Undefined :) The bigger the value the more gets dumped.

Debug/crack/hack some loader? Log is usually enough to find out where it is called.

I try to understand:

first line:
DSKLEN: - info label, like SYNC:
drive 0 - ok, it's df0:
motor on - motor state
cylinder 0 - track 0, side 0 (info)
sel yes rw - ?
mfmpos 52533/101344 - ok, current bit position

total length: 101344?
1 track = 11*512 Bytes*8= 45056 Bits
MFM=11*(2*(64Byte+512Byte))*8=101376 Bits

second line:
data - 17 words, mfm data (but not synchronized)
data are not from the beginning of a track?
the current position stands anywhere? like here: 52533?
(Then a breakpoint for a certain mfmpos would be good?
To analyze mfm-data from beginning of a track)

| = current position - ok, from the raw bit stream dump

third line:
side 0 - ok, see cylinder 0
dma 2 - ? dma is always 2?
off 1 - ? off with different numbers from 1 to 13?
word 5555 - ok, current value
pt 00002064 - DSK pointer ($dff020,22 DSKPTH, DSKPTL)
len 9CBE - ok, length ($dff024 DSKLEN)
bytr 80AA - ok, DSKBYTR ($dff01A DSKBYTR)
adk 1100 - ok, ADKCON ($dff010 ADKCONR)
sync 0000 - ok, DSKSYNC ($dff07E DSKSYNC)

SYNC: drive 0 motor on cylinder 69 sel yes rw mfmpos 5648/101344
AAAA AAAA AAAA 4489|4489 5545 2AA5 552A AAA9 2AAA AAAA AAAA AAAA AAAA AAAA AAAA AAAA
side 0 dma 2 off 0 word 4489 pt 00070000 len 9F40 bytr 8044 adk 1500 sync 4489

What means SYNC?
It's this preamble and syncword? AAAA AAAA 4489|4489
But why there are three times AAAA AAAA AAAA and not only 2 times?

Drive selected (yes) or not selected (no). (SEL0-SEL3 bits)

Total number of bits in this track.

It is theoretical max bits that Amiga can write. It is not logical floppy format size.

PAL: 3546895 / (7 * 5)
NTSC: 3579545 / (7 * 5)

(7 = clocks per bit, 5 = 5 revs/second)

DMA state.
0 = off.
1 = first DSKLEN write only done.
2 = read DMA active.
3 = write DMA active.

Current bit position in current loaded word. (Not very useful)

It means debug log message was caused by DSKSYNC match. Another possibility is DSKLEN write (DMA started).


It always shows last 4 words. Nothing to do with sync.

thank you for the information.

What I'm missing at the end is an example of what it could be useful.
So, how I have to interpret the raw bit stream data?

I see no connection between the data on an adf file and the raw bit stream.
I also don't get a connecetion between the current bitposition 98972 and to the hex data, e.g. of an adf file.

Learn how Amiga MFM encoding works :)

WinUAE does not care or need to know. Raw bit stream is DMA'd to memory. MFM decoding is done by Amiga side software (trackdisk.device or game/demo trackloader).

In theory UAE could decode it but it would return garbage if format is not standard AmigaDOS.