Docs » Autodocs » trackdisk.device » TD_RAWWRITE
TD_RAWWRITE/ETD_RAWWRITE -- write raw data to the disk.
This command writes a track of raw data from the provided buffer to
the specified track on disk. The data is copied straight to the disk
with no processing done on it. It will appear exactly on the disk as
it is in the memory buffer, hopefully in a legal MFM format.
This interface is intended for sophisticated programmers only.
Amiga reserves the right to make enhancements to the disk
format in the future. We will provide compatibility via the
CMD_WRITE and ETD_WRITE commands, anyone using TD_RAWWRITE is
bypassing this upwards compatibility, and may thus stop working.
IO REQUEST INPUT
io_Device preset by the call to OpenDevice()
io_Unit preset by the call to OpenDevice()
io_Command TD_RAWWRITE or ETD_RAWWRITE.
io_Flags if the IOTDB_INDEXSYNC bit is set then the driver
will make a best effort attempt to start writing
from the index mark. Note that there will be at
least some delay, and perhaps a great deal of delay
(for example if interrupts have been disabled).
io_Length Length of buffer in bytes, with a maximum of 32768
io_Data Pointer to CHIP memory buffer where raw track data is
to be taken.
io_Offset The number of the track to write to.
iotd_Count (ETD_RAWWRITE only) maximum allowable change counter
IO REQUEST RESULT
io_Error - 0 for success, or an error code as defined in
The track buffer provided MUST be in CHIP memory
There is a delay between the index pulse and the start of bits
going out to the driver (e.g. write gate enabled). This delay
is in the range of 135-200 microseconds. This delay breaks
down as follows: 55 microsecs is software interrupt overhead
(this is the time from interrupt to the write of the DSKLEN
register). 66 microsecs is one horizontal line delay (remember
that disk IO is synchronized with agnus' display fetches).
The last variable (0-65 microsecs) is an additional scan line
since DSKLEN is poked anywhere in the horizontal line. This leaves
15 microsecs unaccounted for... Sigh.
In short, You will almost never get bits within the first 135
microseconds of the index pulse, and may not get it until 200
microseconds. At 4 microsecs/bit, this works out to be between
4 and 7 bytes of user data of delay.
This command does not work reliably under versions of KickstartTD_RAWREAD()
earlier than V36, especially on systems with 1 floppy drive.