InLine 76660X Internal Serial Adapter M.2 Male 4 Gbit/s

The InLine 76660X internal serial adapter is a compact M.2 card that adds two RS-232 DB9 serial ports to systems with an M.2 (B+M key) slot supporting PCIe. The adapter uses a PCIe 2.0 (5 GT/s) interface and integrates the ASIX AX99100 controller with 16C950 UART compatibility to provide reliable serial communication for industrial and embedded applications. Power is supplied via the M.2 slot (3.3 V); no additional power connection is required. Two low-profile and one high-profile slot bracket are included, together with DB9 cables and mounting screws.

Advantages

The card supports single-lane PCIe 2.0 throughput and automatic lane configuration detection at boot, enabling straightforward installation and integration. With an onboard LED indicator for activity and a 256-byte FIFO buffer, the adapter handles serial data reliably up to the specified transfer rate. The ASIX AX99100 controller provides 16C950 UART compatibility and the device requires no additional driver for common Windows and Linux distributions.

Suitable for

• Industrial control systems and PLC communication
• Embedded systems and single-board computers with M.2 PCIe slots
• Serial devices such as measurement instruments, modems, and legacy equipment

Key specifications

• Interface: M.2 59-pin (B+M key), PCIe 2.0 (single-lane, 5 GT/s)
• Controller: ASIX AX99100 with 16C950 UART compatibility
• Ports: 2 × RS-232 DB9 (9-pin)
• Maximum serial transfer rate: up to 1 Mb/s
• Data bits: 5, 6, 7, 8, 9
• Flow control: None, Xon/Xoff, RTS/CTS
• Parity: even, odd, none, mark, space
• FIFO buffer: 256 bytes
• Power: 3.3 V via M.2 slot
• Operating temperature: -40 °C to +85 °C
• Dimensions: 22 mm × 80 mm (M.2 board)

How to use

Install the InLine 76660X into an available M.2 slot (B+M key) on a motherboard that supports PCIe. Secure the card with the included screw and select the appropriate low- or high-profile bracket for the system chassis. Connect serial devices to the two DB9 ports using the supplied DB9 cables. The adapter draws power from the M.2 slot; no external power connection is necessary. On supported operating systems (Windows 11–XP and Linux kernel 2.6.31 or newer), the device is recognized without additional drivers.

Usage recommendations

For reliable serial communication, use shielded DB9 cables where appropriate and ensure the host motherboard BIOS is configured to enable M.2 PCIe endpoints. Verify operating system compatibility before installation and place the card in a slot that provides sufficient airflow to meet the specified operating temperature range.