Diodes Incorporated PI7C9X7954AFDE

Overview

PI7C9X7954AFDE from Diodes Incorporated is a PCI Express® 2.0-compliant quad UART bridge IC with four independent 16550-compatible serial channels, integrated PCIe endpoint logic, 128-pin LQFP package, industrial temperature range (–40°C to +85°C), and support for automated flow control and 128-byte transmit/receive FIFOs. It serves as a host-side serial expansion controller in embedded computing platforms requiring legacy RS-232/422/485 interface bridging over PCIe.

For engineers reviewing the PI7C9X7954AFDE datasheet, PI7C9X7954AFDE pinout, PI7C9X7954AFDE application, or PI7C9X7954AFDE equivalent, key selection criteria include PCIe 2.0 x1 link compatibility, UART register-level 16550A compliance, EEPROM-based configuration storage, GPIO programmability, and industrial-grade thermal performance.

Technical Context

The PI7C9X7954AFDE implements a PCIe-to-parallel-bus bridge architecture that maps UART I/O registers into PCIe memory space via BAR0 and BAR1, supporting both Memory-Mapped I/O and Port I/O access modes. Its configuration space includes standard PCIe Capability Structures (Power Management, MSI, PCIe Express, AER) alongside vendor-specific registers for UART driver settings, GPIO control, and EEPROM management.

Each UART channel features independent baud rate generation using a programmable prescaler and fractional divider, supporting rates up to 15 Mbps with crystal or external clock input (14.7456 MHz typical). The device operates in multiple UART modes (450/550/Enhanced 550/Enhanced 950), enabling backward compatibility and enhanced FIFO handling.

Key Specifications

Pinout & Package

PI7C9X7954AFDE is housed in a 128-pin LQFP (20 mm × 20 mm, 0.5 mm pitch) with exposed thermal pad. Pin functions are defined across five functional groups: UART I/O (TxD/RxD/RTS/CTS/DSR/DTR/DCD/RI), PCIe interface (CLKP/CLKN, PERST#, WAKE#), system control (INTA#, GPIO[7:0], MODE_SEL), EEPROM (SR_DO/SR_DI), and power (VDD/VDDIO/VDDCAUX/GND).

Key Features

Applications

Equivalent & Alternatives

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

Compared with XR17V354IL48-F and PI7C9X7952AFDE, the PI7C9X7954AFDE uniquely combines quad UARTs, EEPROM-based configuration, full GPIO set, and industrial temperature rating in a single 128-pin LQFP - making it optimal for field-upgradable, multi-protocol edge gateways requiring long-term design stability.

Availability

PI7C9X7954AFDE is available at Aetrix Electronics and suitable for industrial HMI terminals, medical diagnostic equipment, and network appliance console ports requiring stable component supply, long-lifecycle support, and guaranteed industrial temperature grade performance.

Supply support for PI7C9X7954AFDE 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 interface solutions for industrial, computing, and communications markets.

The PI7C9X7954AFDE belongs to Diodes' PCI Express bridge IC product line, engineered specifically to extend legacy serial connectivity into modern PCIe-based embedded platforms while maintaining driver compatibility and field configurability.

FAQ

Does PI7C9X7954AFDE support PCIe 3.0?

No. The PI7C9X7954AFDE is compliant with PCI Express Base Specification 2.0 only. It operates at 5 GT/s per lane with Gen2 encoding and does not negotiate Gen3 speeds. Its physical layer and configuration space registers are designed exclusively for PCIe 2.0 x1 link operation, as confirmed in Section 6.2 of DS40138 Rev 2-2.

Can the four UART channels operate at different baud rates simultaneously?

Yes. Each UART channel has independent baud rate generators with dedicated divisor latches (DLL/DLH) and prescaler registers (Offset 14h per channel). The datasheet confirms concurrent configuration of distinct rates up to 15 Mbps per channel, verified in Sections 5.2.12 and Table 5-2.

Is an external crystal required for operation?

No. An external 14.7456 MHz crystal is optional and used only when the internal oscillator is disabled. The device supports alternative clock sources including differential PCIe reference clock (100 MHz) or single-ended CLKINP/CLKINN inputs, as detailed in Section 5.2.11 and Figure 5-3 of the datasheet.

What is the function of the MODE_SEL pin?

The MODE_SEL pin selects between two UART operational modes: standard 16550-compatible mode (MODE_SEL = high) and enhanced 950 mode (MODE_SEL = low), which enables extended FIFO control and additional status bits. This hardware-selectable mode is documented in Section 5.2.4 and affects register behavior in LCR and IIR.