The ATA 50-to-40-pin adapter connects a slim ATAPI optical drive — typically a notebook CD-ROM or DVD-ROM unit — to a standard 40-pin ATA/IDE host bus. The ATA/IDE interface (governed by the T13 technical committee, with the core 40-pin signal set normatively defined in ATA/ATAPI-5, T13/1321D, 2000) uses a 2.54 mm pitch IDC header on the host side. The slim 50-pin connector found on notebook optical drives is a proprietary mechanical form factor, commonly associated with JAE or Hirose variants, and integrates power supply lines (+5 V on pins 38–42) and analogue audio outputs (left, right, and audio ground on pins 1–3) alongside the standard ATA signal set, eliminating the need for a separate power connector. This adapter maps each ATA signal on the 40-pin side to its corresponding pin on the 50-pin drive connector.
40 PIN IDC FEMALE at the cable
50 pin connector at the notebook CD-ROM device
| ATA (40) Pin | CD-ROM (50) Pin | Name | Description |
|---|---|---|---|
| 1 | Audio Left | audio left | |
| 2 | Audio Right | audio right | |
| 3 | Audio ground | audio ground | |
| 2 | 4 | GND | Ground |
| 1 | 5 | /RESET | Reset |
| 4 | 6 | DD8 | Data 8 |
| 3 | 7 | DD7 | Data 7 |
| 6 | 8 | DD9 | Data 9 |
| 5 | 9 | DD6 | Data 6 |
| 8 | 10 | DD10 | Data 10 |
| 7 | 11 | DD5 | Data 5 |
| 10 | 12 | DD11 | Data 11 |
| 9 | 13 | DD4 | Data 4 |
| 12 | 14 | DD12 | Data 12 |
| 11 | 15 | DD3 | Data 3 |
| 14 | 16 | DD13 | Data 13 |
| 13 | 17 | DD2 | Data 2 |
| 16 | 18 | DD14 | Data 14 |
| 15 | 19 | DD1 | Data 1 |
| 18 | 20 | DD15 | Data 15 |
| 17 | 21 | DD0 | Data 0 |
| 21 | 22 | DMARQ | DMA Request |
| 19 | 23 | GND | Ground |
| 25 | 24 | /DIOR | Read Strobe |
| 23 | 25 | /DIOW | Write Strobe |
| 22 | 26 | GND | Ground |
| 27 | 27 | IORDY | I/O Ready |
| 29 | 28 | /DMACK | DMA Acknowledge |
| 31 | 29 | INTRQ | Interrupt Request |
| 32 | 30 | /IOCS16 | IO ChipSelect 16 |
| 33 | 31 | DA1 | Address 1 |
| 34 | 32 | PDIAG | Passed Diagnostics |
| 35 | 33 | DA0 | Address 0 |
| 36 | 34 | DA2 | Address 2 |
| 37 | 35 | /IDE_CS0 | (1F0-1F7) |
| 38 | 36 | /IDE_CS1 | (3F6-3F7) |
| 39 | 37 | /ACTIVE - /DASI - DASP | Led driver |
| +5V | 38 | +5V | + 5 volts power |
| +5V | 39 | +5V | + 5 volts power |
| +5V | 40 | +5V | + 5 volts power |
| +5V | 41 | +5V | + 5 volts power |
| +5V | 42 | +5V | + 5 volts power |
| 24 | 43 | GND | Ground |
| 26 | 44 | GND | Ground |
| 30 | 45 | GND | Ground |
| 40 | 46 | GND | Ground |
| 28 | 47 | Device Cfg | Spindle Sync or Cable Select |
| GROUND | 48 | GND | Ground |
| 49 | reserved | Vendor Unique | |
| 50 | reserved | Vendor Unique |
Notes
- The 40-pin IDC host connector follows the standard ATA pin assignment; pin 20 is keyed/removed.
- Power (+5 V) is supplied via the 50-pin connector (pins 38–42); no separate Molex power connector is used.
- Analogue audio output (pins 1–3 on the 50-pin side) has no equivalent on the standard 40-pin ATA bus and is carried only on the 50-pin side of the adapter.
- The slim 50-pin connector is a proprietary mechanical form factor; no single industry-wide standard governs its dimensions across all manufacturers.
- Pins 49 and 50 on the 50-pin connector are reserved for vendor-unique functions.
- The standard ATA 16-bit data bus (DD0–DD15) and 3-bit address bus (DA0–DA2) are wired straight through to their ATA counterparts.
Signals
- /RESET — Hardware reset; asserted low by the host to initialise the drive.
- DD0–DD15 — 16-bit bidirectional data bus.
- DMARQ — DMA request; asserted by the device to request a DMA transfer.
- /DIOR — I/O read strobe; asserted low by the host to read a register or data.
- /DIOW — I/O write strobe; asserted low by the host to write a register or data.
- IORDY — I/O ready; the device drives this low to insert wait states.
- /DMACK — DMA acknowledge; asserted low by the host to acknowledge a DMA transfer.
- INTRQ — Interrupt request; asserted by the device to signal command completion.
- /IOCS16 — Chip select for 16-bit I/O; indicates 16-bit data transfer cycle.
- DA0–DA2 — 3-bit address bus for register selection.
- PDIAG — Passed diagnostics; used in device-to-device communication.
- /IDE_CS0 — Chip select 0; decodes the command block registers (1F0h–1F7h).
- /IDE_CS1 — Chip select 1; decodes the control block registers (3F6h–3F7h).
- /ACTIVE (/DASP) — Device active / slave present; drives an LED indicator or indicates Device 1 presence.
- Device Cfg — Spindle synchronisation or cable select; function depends on drive configuration.
- GND — Signal and power ground.
- +5V — +5 V power supply (pins 38–42 on the 50-pin connector).
- Audio Left / Audio Right / Audio Ground — Analogue audio output from the optical drive (pins 1–3 on the 50-pin connector); not present on the 40-pin ATA bus.