CD-ROM Slimline 68 pin

68 pin Slimline connector at the computer.

The 68-pin slimline connector is a compact ATA/ATAPI host interface used in notebook computers and slim-desktop optical drives from roughly 1997 onward. Unlike the proprietary Panasonic/MKE, Mitsumi, and Sony interfaces of the early 1990s, it carries standard ATA/ATAPI signals — including DRQ, IOW, IOR, IOCHRDY, IRQ, CS1FX, CS3FX, DA0–DA2, DASP, and PDIAG — making it electrically a physically smaller form of the 44-pin ATA bus used in notebook hard drives. Pins 1–40 map to the ATA/ATAPI signal set, pins 41–47 provide embedded power (+5 V motor and logic) together with analogue audio outputs, and pins 48–68 carry front-panel or OEM-specific signals (labelled FP01–FP21) that were used by Compaq and other slim-desktop OEM system builders.

Notes

• The slimline 68-pin connector integrates the ATA/ATAPI signal bus (pins 1–40), power rails (pins 41–42), and analogue audio (pins 44–47) in a single keyed header, eliminating the separate power and audio cables required by full-size 5.25-inch drives.
• Pin 20 is physically keyed (absent or blocked) to prevent incorrect cable orientation.
• The ATA/ATAPI signal set on pins 1–40 is electrically compatible with the standard 44-pin ATA interface used in notebook hard drives; cable-select behaviour is governed by pin 28 (CABLE SELECT).
• Pins 48–68 (FP01–FP21) carry OEM-defined front-panel or system-management signals; their assignment is manufacturer-specific and not part of the ATA/ATAPI standard — Compaq and other slim-desktop vendors used these for eject buttons, busy indicators, and chassis-management lines.
• The connector is not compatible with the proprietary Panasonic/MKE, Mitsumi, or Sony CD-ROM interfaces, which use separate 40-pin or 34-pin IDC ribbon cables and entirely different signalling.

Signals

• /RESDRV — ATA reset; active-low signal that resets the drive; equivalent to /RESET on the standard 44-pin ATA connector.
• DO7–D00 / DO8–D15 — 16-bit ATA/ATAPI data bus (pins 3–18); pin order interleaves low byte (D00–D07) and high byte (D08–D15) across odd/even pairs.
• DRQ — DMA or PIO data request; asserted by the drive when it is ready to transfer a data word.
• IOW — I/O write strobe; host asserts to write a data word or register to the drive.
• IOR — I/O read strobe; host asserts to read a data word or register from the drive.
• IOCHRDY — I/O channel ready; drive de-asserts to insert wait states when it cannot complete a cycle at standard speed.
• CABLE SELECT — cable-select line; determines device master/slave role from the cable wiring rather than jumper settings when the drive is configured for cable-select mode.
• DAK — DMA acknowledge; host asserts in response to DRQ to initiate a DMA transfer cycle.
• IRQ — interrupt request; drive asserts to signal the host that a command has completed or an attention condition exists.
• IO16 — 16-bit I/O indicator; drive asserts to indicate it supports 16-bit data transfers.
• A0, A1, A2 — address lines DA0–DA2; host drives these to select a drive register for read or write access.
• CS1FX — chip select for the primary ATA register block (I/O base address, e.g. 0x1F0–0x1F7).
• CS3FX — chip select for the alternate status/device-control register block (e.g. 0x3F6–0x3F7).
• DASP — drive active / slave present; dual-purpose open-collector line used during reset to indicate a slave device is present, and during operation to signal drive activity.
• PDIAG — passed diagnostics; asserted by the slave drive after successful completion of self-diagnostics, sampled by the host and master drive.
• +5VMLOG — +5 V logic supply for drive electronics.
• +5VMOT — +5 V motor supply for the spindle and disc-loading mechanism.
• AUDIO_L — left-channel analogue audio output from the optical drive’s digital-to-analogue converter; carries CD-DA audio for connection to the system’s audio subsystem.
• AUDIO_R — right-channel analogue audio output.
• A_GROUND_L — analogue ground reference for the left audio channel.
• A_GROUND_R — analogue ground reference for the right audio channel.
• FP01–FP21 — OEM/front-panel signals (pins 48–68); functions are manufacturer-defined and not standardised; typically used for eject control, activity LEDs, and OEM system-management in Compaq and similar slim-desktop platforms.

References

• ATA Packet Interface for CD-ROMs — SFF-8020 Rev 1.2 — SFF Committee; the ATAPI command/signal set carried on pins 1–40 of this connector.
• T13 AT Attachment — Standards (Expired/Withdrawn) — INCITS Technical Committee T13; the underlying ATA register/signal set shared with the 44-pin notebook interface.

Category:Data Storage Connectors