Notes for the Sigma Disk Controllers

Two patterns of disk controllers - "10 byte" sense controllers and "16 byte" sense controllers
All disks have 1024B (256W) sectors


model			units/cylinders/heads/sectors		type

7240/7242		8  / 203 (3 spare) / 20 / 6		10 byte		24360
7260/7261		15 / 203 (3 spare) / 20 / 11		16 byte		44660
7270/7271		8  / 406 (6 spare) / 20 / 6		10 byte		48720
7275/7276		15 / 411 (7 spare) / 19 / 11		16 byte		85899
7265/7266		15 / 411 (7 spare) / 20 / 11		16 byte		90420

T3281/T3282		15 / 815 / 19 / 11			16 byte		170335
T3281/T3283		15 / 815 / 19 / 17			16 byte		263245
T3281/T3286		15 / 555 / 30 / 17 (16?)		16 byte
T3281/T3286F		15 / 555 / 60 / 17 (16?)		16 byte
T3281/T3288		15 / 822 / 5 / 17			16 byte		69870	

header format		7240				726X/727X/T3281

bytes 0-3		flaw / 0 / C / H		flaw / 0'CH / C / H
bytes 4-7		S / alt C / alt H / 0		S / alt CH / alt CL'alt H / 0


sense status		7240/7270

bytes 0-3		0'CH / C / H / S		most recent address
bytes 4-7		M'CS / diag / diag / diag	seek intr + current sector
bytes 8-11		stat / stat

			726X/7275

bytes 0-3		W'0'CH / C / H / S		W = write protect, most recent address
bytes 4-7		M'R'CS / cnf / stat / 0		M = modifier, R = reserve/release mode
bytes 8-11		stat / stat / modi / fiers
bytes 12-15		check / bytes / 0'dh / dl	14-15 = difference

sense byte 5-6

	7240,7270

0-15	header parity check bytes

	726X, 7275, T3281

0	1 for dual access
1-3	device type
	5 = 7261
	6 = 7266
	7 = 7276, T3286
4-7	device physical addr (cable position)

0	device fault
1	write fault
2	loss of on cylinder
3	offset polarity
4	airflow loss
5	parity error on device ID byte
6	spindle speed fault
7	positioning servo faulT

sense byte 7

	7240, 7270		726X, 7275		T3281

0-7	LSB of difference	0			physical address (unique)

sense bytes 8-9

	7240, 7270		726X, 7275, T3281

0	data parity error	check write error
1	check write error	data check error
2	sector verif error	IOP parity error
3	head verif error	data overrun
4	cylinder verif error	head addr incr err
5	sec addr !=0 @ hdr wr	arm in motion err
6	diff sent to device	order parity err
7	sector sel to device	test mode err

0	ctrl sel to device	seek transfer err
1	head sel to device	device unavailable
2	cyl sel sent to device	head addr ver err
3	seek forward set	sector addr ver err
4	read gate to device	cyl addr ver err
5	write/erase to device	726X, 7275: 0
				T3281: ctrl overtemp
6	read cyl sel to device	channel addr err
7	7240: not used		missing on sect
	7270: MSB of diff

sense bytes 10+

10-11	modifier bits
12-13	check bytes
14	0'diff high
15	diff low (absolute value)


operations			7240	726X
				7270	7275
					T3281

01	write			x	x
02	read 2			x	x
03	seek			x	x
04	sense			x	x
05	check-write		x	x
07	reserve				x
09	header write		x	x
0A	header read		x	x
0F	condition rls intr		x
12	read 1			x	x
13	select test mode	x	x
17	release				x
1F	condition rls intr		x
23	release			x
33	restore			x	x
83	seek with interrupt	x	x
B3	restore with interrupt		x


TIO, SIO, HIO status

	all

0	interrupt pending
1-2	device state
	00 = ready
	01 = not operational
	10 = reserved
	11 = busy
3	1 (automatic)
4	unusual end
5-6	controller state
	00 = ready
	01,10 = n/a
	11 = busy
7	0

TDV status

	7240, 7270		726X,7275		T3281

0	data overrun		0			error corrected
1	flaw mark		flaw mark		flaw mark
2	sector unavailable	programming err		programming err
3	0			write prot err		write prot err
4	header verif error	IOP parity err		IOP parity err
5	on cylinder		operational err		operational err
6	seek timeout error	verification err	verification err
7	header parity error	header parity err	header parity err

AIO status

	7240, 7270		726X, 7275, T3281

0	data overrun		data overrun
1	0			attn int ack
2	0			rls int ack
3	0			0
4	on sector interrupt	on sector intr
5	on cylinder		0
6	seek timeout error	seek timeout error
7	0			0

operational status byte (SIO, HIO, TIO, TDV)

	all

8	incorrect lnt
9	xmit data error
10	xmit memory err
11	mem addr err
12	IOP memory err
13	IOP ctrl err
14	IOP halt
15	0

operational status byte (AIO)

	all

8	incorrect lnt
9	xmit data error
10	zero byte cnt intr
11	channel end intr
12	unusual end intr
13-15	0


