Diodes Incorporated PI7C9X7954BFDEX

Overview

PI7C9X7954BFDEX from Diodes Incorporated is a PCI Express® 2.0-compliant quad UART controller with integrated PCIe endpoint logic, supporting four independent asynchronous serial channels, 128-byte transmit/receive FIFOs per channel, and programmable baud rates up to 15 Mbps. It operates across industrial temperature range (–40°C to +85°C) and interfaces directly to PCIe x1 links in embedded computing, industrial gateways, and legacy serial peripheral expansion.

For engineers reviewing the PI7C9X7954BFDEX datasheet, PI7C9X7954BFDEX pinout, PI7C9X7954BFDEX application, or PI7C9X7954BFDEX equivalent, key selection criteria include PCIe 2.0 endpoint compliance, UART register compatibility with 16550/16750, FIFO depth configuration, EEPROM-based configuration storage, and support for automated hardware flow control (RTS/CTS).

Technical Context

The PI7C9X7954BFDEX implements a PCIe 2.0 endpoint with Type 0 configuration space, supporting Memory-Mapped I/O (MMIO) and Message Signaled Interrupts (MSI). Its UART subsystem uses standard 16550-compatible register mapping with extended features including enhanced 950-mode operation, clock prescaling, and dynamic FIFO trigger level control.

It integrates a 14.7456 MHz crystal oscillator interface, supports both internal and external clock sources, and includes dedicated GPIO pins for UART control signaling (e.g., RTS, CTS, DTR, DSR). Power management includes L0s/L1 states compliant with PCIe specification, with configurable wake-on-serial-event capability.

Key Specifications

Pinout & Package

PI7C9X7954BFDEX is housed in a 128-pin LQFP package with exposed thermal pad (EP), designed for mechanical stability and thermal dissipation in dense PCB layouts. Pin assignments are defined per DS40138 Rev 2-2 Section 4.1 and validated for PCIe signal integrity and UART noise immunity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad UART PCIe bridge applications.

Compared with XR17V354IL48-F and XR17V352IL48-F, PI7C9X7954BFDEX delivers higher FIFO depth, EEPROM-based configuration, and full industrial temperature support - making it optimal for space-constrained, field-upgradable, and thermally demanding deployments.

Availability

PI7C9X7954BFDEX is available at Aetrix Electronics and suitable for industrial HMI terminals, PCIe serial expansion cards, and medical diagnostic equipment requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for PI7C9X7954BFDEX 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, specializing in high-performance analog, logic, and connectivity solutions for industrial, computing, and communications markets.

The PI7C9X7954BFDEX belongs to Diodes' PCI Express interface product line, engineered specifically to replace legacy parallel-bus UART controllers in modern PCIe-based platforms while maintaining software compatibility and enhancing reliability.

FAQ

Does PI7C9X7954BFDEX require an external crystal oscillator?

No. The device supports both external 14.7456 MHz crystal connection (via CLKINP/CLKINN) and internal oscillator circuitry. When using the internal oscillator, only a single 14.7456 MHz crystal is needed across X1/X2 pins - no external clock generator IC is required. This simplifies layout and reduces BOM count while meeting PCIe 2.0 clock jitter requirements.

Is the PI7C9X7954BFDEX pin-compatible with earlier PI7C9X7952 or PI7C9X7953 variants?

No. PI7C9X7954BFDEX uses a 128-pin LQFP package with distinct pin assignments for PCIe lanes, UART I/O, and power domains. Earlier variants use different packages (e.g., 100-pin QFP for PI7C9X7952) and lack support for enhanced 950 mode, MSI, and EEPROM configuration. Board-level redesign is required for migration.

Can the PI7C9X7954BFDEX operate in legacy PCI mode?

No. PI7C9X7954BFDEX is a native PCIe 2.0 endpoint only and does not support legacy PCI bus protocol, configuration space, or signaling. It requires a PCIe root complex host - no PCI-to-PCIe bridge is supported or necessary. Legacy PCI systems must use discrete PCI UART chips such as the PI7C9X768.

What UART register set does PI7C9X7954BFDEX implement?

It implements full 16550A/16750 register compatibility with extensions for enhanced modes. All standard offsets (e.g., THR/RHR at 00h, IER at 01h, FCR at 02h, LCR at 03h) match industry-standard drivers. Extended registers (e.g., CPRM at 1Ch, ACR at 18h) enable advanced features like clock prescaling and FIFO tuning without breaking OS abstraction layers.