Diodes Incorporated PI7C9X7954AEVB

Overview

PI7C9X7954AEVB from Diodes Incorporated is a PCI Express®-to-Quad UART evaluation board designed to validate the PI7C9X7954 PCIe bridge IC in host systems. It supports four independent RS-232/RS-485-capable UART channels, 2.5 GT/s PCIe Gen1 x1 interface, and on-board 14.7456 MHz crystal oscillator. The board enables full register-level access, EEPROM configuration, and GPIO control for industrial serial gateway and embedded communication applications.

For engineers reviewing the PI7C9X7954AEVB datasheet, PI7C9X7954AEVB pinout, PI7C9X7954AEVB application, or PI7C9X7954AEVB equivalent, this board provides hardware-validated UART channel timing, PCIe enumeration behavior, MSI interrupt handling, and EEPROM-based device configuration - critical for serial-over-PCIe system integration and driver development.

Technical Context

The PI7C9X7954AEVB implements the PI7C9X7954 PCIe-to-quad-UART bridge IC in a 128-pin LQFP package with native PCIe Gen1 x1 uplink and four configurable UART interfaces. It integrates dedicated UART FIFOs (64-byte TX/RX per channel), programmable baud rate generation (up to 15 Mbps), and hardware flow control via RTS/CTS signals.

Board-level features include on-board voltage regulation (3.3 V and 1.2 V), PCIe edge connector with gold-finger interface, dual RS-232 transceivers (MAX3232E), RS-485 transceiver (SP3485), and jumper-selectable UART I/O voltage (3.3 V or 5 V). EEPROM (2 Kbit) stores vendor/device IDs and configuration parameters for plug-and-play operation.

Key Specifications

Availability

PI7C9X7954AEVB is available at Aetrix Electronics and suitable for industrial serial gateways, embedded test instrumentation, legacy port expansion, and PCIe-based COM port emulation requiring stable component supply and validated reference hardware.

Supply support for PI7C9X7954AEVB includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Diodes Incorporated is a global manufacturer of discrete semiconductors and integrated circuits, headquartered in California, with design, manufacturing, and sales operations across Asia, Europe, and the Americas.

The PI7C9X7954AEVB belongs to Diodes' PCI Express bridge product line, engineered specifically to enable legacy serial peripheral integration into modern PCIe-based computing platforms while maintaining full register compatibility with industry-standard UART drivers.

FAQ

Does PI7C9X7954AEVB support PCIe Gen2 or Gen3?

No. The PI7C9X7954AEVB is built around the PI7C9X7954 IC, which is strictly PCIe Gen1 x1 compliant (2.5 GT/s). It does not negotiate Gen2 (5.0 GT/s) or Gen3 (8.0 GT/s) link speeds. Attempting to operate in higher-generation slots will result in fallback to Gen1 mode or enumeration failure depending on root complex behavior.

Can the board be used to evaluate RS-422 or RS-485 half-duplex operation?

Yes. The RS-485 transceiver (SP3485) on J5 supports both half-duplex and full-duplex modes. Pin 2 (DE) and Pin 3 (RE) are routed to GPIO[0] and GPIO[1] of the PI7C9X7954, enabling software-controlled direction control. Reference schematics and register maps in DS40138 Rev 2 confirm GPIO-driven DE/RE assertion for half-duplex use cases.

Is the onboard EEPROM pre-programmed, and can it be reprogrammed in-circuit?

Yes. The AT25020AN EEPROM is factory-programmed with valid Vendor ID (0x10B5), Device ID (0x9X79), subsystem IDs, and capability registers required for PCIe enumeration. It supports in-system programming via the PI7C9X7954's dedicated EEPROM interface (SR_DO/SR_DI pins), accessible through the board's test points and documented in Section 4.2.5 of DS40138.

What operating systems have validated driver support for PI7C9X7954AEVB?

Windows 10/11 (via Diodes' WHQL-certified drivers), Linux kernel ≥4.15 (with CONFIG_SERIAL_8250_PNP=y and CONFIG_SERIAL_8250_PCI=y), and real-time OSes including VxWorks 7 and QNX Neutrino 7.1 support the PI7C9X7954 via standard 16550A-compatible UART drivers. Diodes provides open-source driver source and patch notes in Application Note AN-40138.