The standard command set of 1050 (810) drives:

$52	R	Read sector
$50	P	Write sector
$57	W	Write sector with verify
$53	S	get controller status, returns 4 bytes
	byte 0	drive status
		bit 0 - Command frame error
		bit 1 - Checksum error
		bit 2 - Operation error
		bit 3 - Write protect
		bit 4 - Motor on
		bit 5 - double density
		bit 6 - unused
		bit 7 - Dual (medium) density
	byte 1	controller status, returned values are inverted
		bit 0 - busy
		bit 1 - drq
		bit 2 - lost data
		bit 3 - crc error
		bit 4 - record not found
		bit 5 - record type
		bit 6 - write protect
		bit 7 - not ready
	byte 2 time-out (format); $e0
	byte 3 unused; always 0
$21	!	format disk (single for 810 and stock 1050)
		as defined by CMD $4f for upgraded 1050 and XF 551
		(heard, that they will give back 128/256 bytes?)
$22	"	format enhanced (medium, dual) density (1050)

Special 1050 diagnostic commands:

$23		special diagnostic command, must be followed by CMD $24
		first byte is the command
	$00	RPM-measurement
	$01	motor speed-up time
	$02	step-rate
	$03	do half-steps
	$04	write-test
	$05	seek on track
$24		get results of $23 CMD

These are supported by all double density drives:

$4e	N	read drive configuration; returns 12 bytes
	byte 0	number of tracks [1 for harddisks)
	byte 1	step rate
	byte 2	sectors/track high (total number for harddisks)
	byte 3	sectors/track low 
	byte 4	number of heads decreased by one
	byte 5	format (0=FM; 4=MFM)
	byte 6	bytes/sector high
	byte 7	bytes/sector low
	byte 8	drive activated
	bytes 9-11 unused
$4f	O	write drive configuration; see above
$3f	?	get high-speed-index
		Happy, US-Doubler, HDI (Germany) return $0a
		Speedy (Germany) returns $09

Special Speedy (Germany) commands:
$20		format automatically, acts like $21, but computer has not to wait until drive is ready
$51		stop write command, writes all data from internal buffer to disk, stop motor then
$44		configure drive/track display
$4b		configure slow/fast
$4c		direct jump command for internal processor of 1050
		jumps to location stored in DAUX, $30a
$4d		jump, as above, but drive sends a "COMPLETE" before jumping
$41		add/remove command to/from internal command table
$68		get length of internal high-speed-SIO-subroutine
$69		send high-speed-SIO-routine to computer
$60		write track, writes complete track
$62		read track

US-Doubler:
$66		format disk with special sector-skew