80 pin SCSI SCA-2 female connector.
Drive connector: AMP Champ 557613-1 or AMP Champ 557114-5
Cable connector: AMP Champ 2-557103-1 or AMP Champ 2-557101-1
The SCA-2 (Single Connector Attachment 2) 80-pin connector is a SCSI-3 backplane interface that combines the full 68-pin wide SCSI signal set with power supply rails (+5 V, +12 V, +3.3 V), grounds, DIFFSENSE, TERMPWR, and drive address bits in a single miniature D-style housing. Defined to support hot-plug operation in server backplanes and RAID enclosures, it carries either Single-Ended (SE) or Low Voltage Differential (LVD) SCSI signalling; in SE mode bus cable length is limited to 3 m at Ultra speeds or 6 m at Slow/Fast speeds. The connector superseded the practice of fitting separate power and signal connectors to 3.5-inch SCSI drives, and was widely used from the mid-1990s onwards in enterprise storage systems supporting SCSI-3 parallel interface standards up to Ultra160 and beyond.
| Pin | Name | Dir | Description |
|---|---|---|---|
| 1 | 12V | - | +12 VDC |
| 2 | 12V | - | +12 VDC |
| 3 | 12V | - | +12 VDC |
| 4 | 12V | - | +12 VDC |
| 5 | 3.3V | - | +3.3 VDC |
| 6 | 3.3V | - | +3.3 VDC |
| 7 | -DB(11) | IN/OUT | Data Bus 11 |
| 8 | -DB(10) | IN/OUT | Data Bus 10 |
| 9 | -DB(9) | IN/OUT | Data Bus 9 |
| 10 | -DB(8) | IN/OUT | Data Bus 8 |
| 11 | -I/O | OUT | Input/Output |
| 12 | -REQ | OUT | Request |
| 13 | -C/D | OUT | Control/Data |
| 14 | -SEL | IN/OUT | Select |
| 15 | -MSG | OUT | Message |
| 16 | -RST | IN/OUT | Reset |
| 17 | -ACK | IN | Acknowledge |
| 18 | -BSY | IN/OUT | Busy |
| 19 | -ATN | IN | Attention |
| 20 | -P_CRCA | ? | |
| 21 | -DB(7) | IN/OUT | Data Bus 7 |
| 22 | -DB(6) | IN/OUT | Data Bus 6 |
| 23 | -DB(5) | IN/OUT | Data Bus 5 |
| 24 | -DB(4) | IN/OUT | Data Bus 4 |
| 25 | -DB(3) | IN/OUT | Data Bus 3 |
| 26 | -DB(2) | IN/OUT | Data Bus 2 |
| 27 | -DB(1) | IN/OUT | Data Bus 1 |
| 28 | -DB(0) | IN/OUT | Data Bus 0 |
| 29 | -DB(P1) | ? | |
| 30 | -DB(15) | IN/OUT | Data Bus 15 |
| 31 | -DB(14) | IN/OUT | Data Bus 14 |
| 32 | -DB(13) | IN/OUT | Data Bus 13 |
| 33 | -DB(12) | IN/OUT | Data Bus 12 |
| 34 | 5V | - | Ground (Signal) |
| 35 | 5V | - | Ground (Signal) |
| 36 | 5V CHARGE | - | Ground (Signal) |
| 37 | SPINDLE SYNC | ? | Spindle Sync |
| 38 | RMT_START | ? | Remote Start |
| 39 | SCSI ID (0) | - | SCSI ID Bit 0 |
| 40 | SCSI ID (2) | - | SCSI ID Bit 2 |
| 41 | 12V GROUND | - | +12 VDC Ground |
| 42 | 12V GROUND | - | +12 VDC Ground |
| 43 | 12V GROUND | - | +12 VDC Ground |
| 44 | MATED 1 | ? | |
| 45 | 3.3V CHARGE | - | +3.3 VDC Charge |
| 46 | GROUND | - | Ground |
| 47 | SIGNAL RETURN | - | Ground (Signal) |
| 48 | SIGNAL RETURN | - | Ground (Signal) |
| 49 | SIGNAL RETURN | - | Ground (Signal) |
| 50 | SIGNAL RETURN | - | Ground (Signal) |
| 51 | SIGNAL RETURN | - | Ground (Signal) |
| 52 | SIGNAL RETURN | - | Ground (Signal) |
| 53 | SIGNAL RETURN | - | Ground (Signal) |
| 54 | SIGNAL RETURN | - | Ground (Signal) |
| 55 | SIGNAL RETURN | - | Ground (Signal) |
| 56 | SIGNAL RETURN | - | Ground (Signal) |
| 57 | SIGNAL RETURN | - | Ground (Signal) |
| 58 | SIGNAL RETURN | - | Ground (Signal) |
| 59 | SIGNAL RETURN | - | Ground (Signal) |
| 60 | SIGNAL RETURN | - | Ground (Signal) |
| 61 | SIGNAL RETURN | - | Ground (Signal) |
| 62 | SIGNAL RETURN | - | Ground (Signal) |
| 63 | SIGNAL RETURN | - | Ground (Signal) |
| 64 | SIGNAL RETURN | - | Ground (Signal) |
| 65 | SIGNAL RETURN | - | Ground (Signal) |
| 66 | SIGNAL RETURN | - | Ground (Signal) |
| 67 | SIGNAL RETURN | - | Ground (Signal) |
| 68 | SIGNAL RETURN | - | Ground (Signal) |
| 69 | SIGNAL RETURN | - | Ground (Signal) |
| 70 | SIGNAL RETURN | - | Ground (Signal) |
| 71 | SIGNAL RETURN | - | Ground (Signal) |
| 72 | SIGNAL RETURN | - | Ground (Signal) |
| 73 | SIGNAL RETURN | - | Ground (Signal) |
| 74 | MATED 2 | ? | |
| 75 | 5V GROUND | - | +5 VDC Ground |
| 76 | 5V GROUND | - | +5 VDC Ground |
| 77 | ACTIVE LED OUT | ? | |
| 78 | DLYD_START | ? | |
| 79 | SCSI ID (1) | - | SCSI ID Bit 1 |
| 80 | SCSI ID (3) | - | SCSI ID Bit 3 |
Notes
- Direction is relative to the device with respect to the SCSI bus.
- Pins 1–4: +12 VDC supply for drive motor; pins 41–43: +12 VDC return ground.
- Pins 5–6: +3.3 VDC (reserved/NC on many implementations); pin 45: +3.3 V charge (reserved/NC on many implementations).
- Pins 34–35: +5 VDC supply lines; pin 36: 5 V charge rail (sometimes labelled 5 VOLT).
- Pins 75–76: +5 VDC ground return; pins 46–73: signal return (ground) for SCSI signal pairs.
- Pin 20 (-P_CRCA): carries the parity/CRC signal for the lower byte of the wide data bus (equivalent to -DB(P0) in standard 68-pin notation).
- Pin 29 (-DB(P1)): parity bit for the upper byte (DB8–DB15) of the 16-bit wide data bus.
- Pins 39, 40, 79, 80: SCSI ID bits 0–3, used by the backplane to assign a fixed SCSI target ID to each slot without jumpers or switches.
- Pin 37 (SPINDLE SYNC): optional signal allowing the backplane to synchronise spindle rotation across multiple drives to reduce peak power demand.
- Pin 38 (RMT_START): remote start signal, allowing the backplane to sequence drive spin-up.
- Pin 44 (MATED 1) and pin 74 (MATED 2): connector presence-detect signals, asserted when the drive is fully seated; used to control hot-plug power sequencing.
- Pin 77 (ACTIVE LED OUT): open-collector output from the drive indicating I/O activity; drives the backplane activity LED.
- Pin 78 (DLYD_START): delayed start signal, an alternative spin-up sequencing line used by some backplane implementations.
- In Single-Ended mode, DIFFSENSE is held at or near 0 V; LVD/MSE devices read DIFFSENSE to determine bus electrical mode and switch accordingly. Connecting any SE device to an LVD bus downgrades the entire segment to SE mode.
- Active termination is required at both ends of the SCSI bus segment for all speeds above Slow SCSI (5 MB/sec); TERMPWR is supplied through the backplane.
Signals
- -DB(0) to -DB(7) — Lower byte of the 16-bit wide SCSI data bus (active-low, SE signalling).
- -DB(8) to -DB(11), -DB(12) to -DB(15) — Upper byte of the 16-bit wide SCSI data bus.
- -DB(P1) — Odd-parity bit covering the upper data byte (DB8–DB15); direction is IN/OUT.
- -P_CRCA — Parity/CRC-A signal for the lower data byte (equivalent to -DB(P0)); supports CRC checking introduced in Ultra3/Ultra160 (SPI-3).
- -BSY — Bus Busy; asserted by any device using the bus.
- -SEL — Select; used by initiator to select a target or by target during reselection.
- -C/D — Control/Data; driven by target to indicate whether the bus carries command/status/message bytes (high) or data (low).
- -MSG — Message; asserted by target during the message phase.
- -REQ — Request; driven by target to request a data transfer handshake.
- -ACK — Acknowledge; driven by initiator in response to -REQ to complete the handshake.
- -ATN — Attention; driven by initiator to signal the target to enter the message-out phase.
- -RST — Reset; causes all devices on the bus to return to their initial state.
- -I/O — Input/Output; driven by target to define the direction of data transfer relative to the initiator.
- SPINDLE SYNC — Optional backplane signal for coordinated spindle rotation across drives in the same enclosure.
- RMT_START — Remote start; allows the backplane controller to sequence drive spin-up to limit inrush current.
- DLYD_START — Delayed start; an alternative spin-up control line used by some backplane designs.
- SCSI ID (0–3) — Four address bits hardwired by the backplane slot, setting the drive’s SCSI target ID without jumpers.
- MATED 1 / MATED 2 — Presence-detect signals asserted when the drive is fully inserted; used by the backplane for safe hot-swap power sequencing.
- ACTIVE LED OUT — Open-collector I/O activity indicator output; drives the slot activity LED on the enclosure front panel.