Seagate ST36421A, ST32112A, ST38421A, ST34311A manual O pins and supported ATA signals

22				U4 Family Product Manual, Rev. D
Drive pin #	Signal name						Host pin # and signal description
1			Reset–					1			Hardware Reset
2			Ground	2							Ground
3			DD7		3						Host Data Bus Bit 7
4			DD8		4						Host Data Bus Bit 8
5			DD6		5						Host Data Bus Bit 6
6			DD9		6						Host Data Bus Bit 9
7			DD5		7						Host Data Bus Bit 5
8			DD10		8						Host Data Bus Bit 10
9			DD4		9						Host Data Bus Bit 4
10			DD11		10						Host Data Bus Bit 11
11			DD3		11						Host Data Bus Bit 3
12			DD12		12						Host Data Bus Bit 12
13			DD2		13						Host Data Bus Bit 2
14			DD13		14						Host Data Bus Bit 13
15			DD1		15						Host Data Bus Bit 1
16			DD14		16						Host Data Bus Bit 14
17			DD0		17						Host Data Bus Bit 0
18			DD15		18						Device Data (15:0)
19			Ground	19							Ground
20			(removed)	20							(No Pin)
21			DMARQ						21		DMA Request
22			Ground	22							Ground
23			DIOW–						23		Device I/O Write:
			STOP								Stop Ultra DMA Burst
24			Ground	24							Ground
25			DIOR–							25	Device I/O Read:
		HDMARDY–									Host Ultra DMA Ready:
			HSTROBE								Host Ultra DMA Data Strobe
26			Ground	26							Ground
27			IORDY				27				I/O Channel Ready
		DDMARDY–									Device Ultra DMA Ready
			DSTROBE								Device Ulta DMA Data Strobe
28			CSEL							28	Cable Select
29			DMACK–							29	DMA Acknowledge
30			Ground	30							Ground
31			INTRQ			31					Device Interrupt
32			IOCS16–			32					Reserved
33			DA1							33	Host Address Bus Bit 1
34			PDIAG–							34	Passed Diagnostics
			CBLID–								Cable Assembly Type Identifier
35			DA0							35	Device Address (2:0)
36			DA2							36	Device Address (2:0)
37			CS0–							37	Chip Select (1:0)
38			CS1–							38	Chip Select (1:0)
39			DASP–			39					Drive Active/Slave Present
40			Ground	40							Ground

Pins 28, 34 and 39 are used for master-slave communication (details shown below).

Drive 1 (slave)

28

34

39

Drive 0 (master)		Host
28	CSEL	28
34	PDIAG–	34
39	DASP–	39

Figure 4. I/O pins and supported ATA signals