SCSI 68 pin single ended

Pinout of the 68-pin high-density D-Sub SCSI connector used for Wide SCSI (16-bit) in single-ended and LVD/MSE signalling modes.

Updated:

SCSI = Small Computer System Interface

SCSI-3 External Hi D-Sub Low Voltage Differential/Single Ended (LVD/SE)

SCSI 68 pin single ended – 68-pin D-sub female 68 pin hi-density D-SUB female connector at the controller and devices.

SCSI 68 pin single ended – 68-pin D-sub male 68 pin hi-density D-SUB male connector at the cable.

The 68-pin high-density D-Sub (DH68) connector is the standard physical interface for Wide SCSI, carrying a 16-bit data bus (DB0–DB15) plus two parity lines and the full complement of SCSI control signals. Defined in SCSI-2 (ANSI X3.131-1994) and carried forward through SCSI-3 SPI-2 (INCITS 302-1998) to SPI-5 (INCITS 367-2003), it supports Single-Ended (SE), High Voltage Differential (HVD), and Low Voltage Differential / Multimode Single-Ended (LVD/MSE) signalling. LVD/MSE devices automatically detect the bus type via the DIFFSENSE pin and switch between LVD and SE operation accordingly, though connecting any SE device to an LVD bus downgrades the entire bus to SE mode.

PinNameDirDescription
1GND-Ground
2GND-Ground
3GND-Ground
4GND-Ground
5GND-Ground
6GND-Ground
7GND-Ground
8GND-Ground
9GND-Ground
10GND-Ground
11GND-Ground
12GND-Ground
13GND-Ground
14GND-Ground
15GND-Ground
16GND-Ground
17TERMPWRIN/OUTTermination Power
18TERMPWRIN/OUTTermination Power
19RES-Reserved
20GND-Ground
21GND-Ground
22GND-Ground
23GND-Ground
24GND-Ground
25GND-Ground
26GND-Ground
27GND-Ground
28GND-Ground
29GND-Ground
30GND-Ground
31GND-Ground
32GND-Ground
33GND-Ground
34GND-Ground
35-DB12IN/OUT-Data Bus 12
36-DB13IN/OUT-Data Bus 13
37-DB14IN/OUT-Data Bus 14
38-DB15IN/OUT-Data Bus 15
39-DPB1IN/OUT-Data Bus Parity (odd Parity)
40-DB0IN/OUT-Data Bus 0
41-DB1IN/OUT-Data Bus 1
42-DB2IN/OUT-Data Bus 2
43-DB3IN/OUT-Data Bus 3
44-DB4IN/OUT-Data Bus 4
45-DB5IN/OUT-Data Bus 5
46-DB6IN/OUT-Data Bus 6
47-DB7IN/OUT-Data Bus 7
48-DPBIN/OUT-Data Bus Parity (odd Parity)
49GND-Ground
50GND-Ground
51TERMPWRIN/OUTTermination Power
52TERMPWRIN/OUTTermination Power
53RES-Reserved
54GND-Ground
55-ATNIN-Attention
56GND-Ground
57-BSYIN/OUT-Bus is busy
58-ACKIN-Acknowledge
59-RSTIN/OUT-Reset
60-MSGOUT-Message
61-SELIN/OUT-Select
62-C/DOUT-Control or Data
63-REQOUT-Request
64-I/OOUT-In/Out
65-DB8IN/OUT-Data Bus 8
66-DB9IN/OUT-Data Bus 9
67-DB10IN/OUT-Data Bus 10
68-DB11IN/OUT-Data Bus 11

Signals

  • -DB0 – -DB15 — Active-low data bus lines for the 16-bit Wide SCSI data path; all signal names are active-low per SCSI convention.
  • -DPB — Active-low odd parity for the lower data byte (DB0–DB7).
  • -DPB1 — Active-low odd parity for the upper data byte (DB8–DB15).
  • -ATN — Attention; asserted by the initiator to request a message phase with the target.
  • -BSY — Bus Busy; asserted by any device currently using the SCSI bus.
  • -ACK — Acknowledge; asserted by the initiator to confirm receipt of each data byte from the target.
  • -RST — Reset; asserts a hard reset condition on the bus, returning all devices to their initial state.
  • -MSG — Message; asserted by the target during the message phase to distinguish message bytes from command/data bytes.
  • -SEL — Select; used by the initiator to select a target device (or by a target during reselection).
  • -C/D — Control or Data; asserted by the target to indicate whether the current byte is a control (command/message/status) or data byte.
  • -REQ — Request; asserted by the target to request a data transfer handshake cycle.
  • -I/O — In/Out; asserted by the target to indicate the direction of data transfer (asserted = data flowing to initiator).
  • TERMPWR — Termination Power; supplies +5 V to active terminators on the bus; provided by one or more devices on the bus.
  • RES — Reserved; must not be driven and must be left unconnected by compliant devices.
  • GND — Signal ground; the majority of pins are ground to reduce crosstalk and improve signal integrity on the wide connector.

Notes

  • Direction is device-relative to bus (other devices).
  • The connector uses two rows of 34 female contacts at 1.27 mm pitch (female at controller/device, male on cable).
  • In Single-Ended mode, all signal lines are driven against a common ground reference; maximum cable length is 6 m for Slow/Fast SCSI and 3 m for Ultra SCSI.
  • LVD/MSE devices operate at 3.3 V logic and support cable lengths up to 12 m (25 m in point-to-point configurations). They switch to SE mode automatically when a SE device is detected on the bus via the DIFFSENSE pin.
  • HVD (High Voltage Differential) signalling uses complementary +/– signal pairs at 5 V logic and supports cable lengths up to 25 m, but HVD was declared obsolete in SPI-3 (INCITS 336-2000) and must not be mixed with SE or LVD devices.
  • Exactly two terminators are required per bus segment, placed at the two extreme ends only. Passive termination (220/330 Ω resistors) is acceptable only for Slow SCSI (5 MB/s maximum); active termination is required for Fast SCSI and all higher speeds.
  • The DIFFSENSE pin (not explicitly listed in this single-ended pinout) is used by LVD/MSE multimode devices to detect whether the bus is operating in SE or LVD mode.
  • For more information see SCSI Technology.

References

Category:Buses Connectors