Diodes Incorporated PI7C9X752FAEX

Overview

PI7C9X752FAEX from Diodes Incorporated is a dual-channel 16C550-compatible UART IC supporting independent Intel/Motorola bus interfaces, 64-byte TX/RX FIFOs per channel, 5V-tolerant serial inputs, and IrDA 1.0/1.1 encoding/decoding. It operates from 1.62V to 3.6V, delivers up to 16 Mbps serial data rate with 64 MHz clock input, and integrates automatic RTS/CTS hardware flow control with programmable hysteresis - deployed in multi-port RS-232/RS-485 communication cards for factory automation.

For engineers reviewing the PI7C9X752FAEX datasheet, PI7C9X752FAEX pinout, PI7C9X752FAEX application, or PI7C9X752FAEX equivalent, key selection considerations include dual UART independence, 48-pin QFP package compatibility with legacy ISA-style bus designs, RS-485 half-duplex auto-direction control, and software-configurable FIFO trigger levels for DMA-integrated embedded host systems.

Technical Context

The PI7C9X752FAEX implements two fully independent UART channels (A and B), each with its own 16C550 register set, baud rate generator (prescaler ÷1 or ÷4), and dedicated 64-byte transmit/receive FIFOs. Each channel supports programmable RX/TX FIFO trigger levels (via TLR, FCR, or FCTR registers) and real-time FIFO level counters for precise interrupt/DMA coordination.

Hardware flow control is implemented via auto-RTS and auto-CTS with configurable halt/resume thresholds and hysteresis (per Tables A–D), while software flow control supports Xon/Xoff with dual-character sets and optional "Xon Any" resume. The device also embeds IrDA 1.0/1.1 encoder/decoder logic and RS-485 half-duplex direction control output (DLD[6]).

Key Specifications

Pinout & Package

PI7C9X752FAEX is housed in a 48-pin TQFP (7 mm × 7 mm, 0.5 mm pitch) package with exposed thermal pad. Pin functions differ between Intel and Motorola modes, selected by the 16/68# input.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX3100EAP+T and SC16IS752IPW, PI7C9X752FAEX uniquely combines parallel bus flexibility (Intel/Motorola), 5V-tolerant modem I/O, and hardware RS-485 direction control - making it optimal for legacy ISA/PCI add-in cards and industrial backplanes requiring deterministic serial throughput and minimal external components.

Availability

PI7C9X752FAEX is available at Aetrix Electronics and suitable for remote access servers, Ethernet-to-serial bridges, and factory automation controllers requiring stable component supply across extended product lifecycles.

Supply support for PI7C9X752FAEX 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 semiconductor company specializing in discrete, analog, and mixed-signal solutions for industrial, computing, and communications markets.

The PI7C9X752FAEX belongs to Diodes' high-performance communication interface product line, engineered specifically for multi-port serial connectivity in legacy and modern embedded systems demanding reliability, configurability, and pin-compatible upgrade paths.

FAQ

What bus interface modes does PI7C9X752FAEX support, and how is mode selection implemented?

The PI7C9X752FAEX supports both Intel (16-bit ISA-style) and Motorola (68k-style) parallel bus interfaces. Mode selection is controlled by the 16/68# pin: HIGH selects Intel mode (with IOR#, IOW#, CSA#, CSB# active), LOW selects Motorola mode (with R/W#, CS#, A3). Address lines A2–A0 and data bus D7–D0 remain functionally identical in both modes, ensuring design reuse across architectures.

How does the auto RS-485 half-duplex control function, and what register controls it?

The PI7C9X752FAEX provides a dedicated HDX output (pin DLD[6] mapped to OP2A#/OP2B# depending on channel) that automatically asserts during transmit and de-asserts after transmission completes. This behavior is enabled by setting DLD[6] = 1 in the Divisor Latch register (accessed via DLL/DLH with DLAB=1). No external logic or GPIO timing control is needed - the internal state machine synchronizes direction with UART shift register activity.

Can PI7C9X752FAEX operate with a 24 MHz crystal, and what is the maximum achievable baud rate?

Yes - the PI7C9X752FAEX accepts crystal inputs up to 24 MHz on XTAL1, or external clocks up to 80 MHz. With a 24 MHz crystal and prescaler ÷1, the internal baud rate generator supports rates up to ~6.25 Mbps (24 MHz / 16 / 240 ≈ 6.25 Mbps). Using a 64 MHz external clock and 4× sampling yields the full 16 Mbps capability, as confirmed in DS40312 Rev 3-2 Section 1.

What is the purpose of the "Xon Any" feature, and how is it enabled?

The "Xon Any" feature (MCR[5]) allows any received character to resume transmission after an Xoff condition - eliminating dependency on specific Xon characters in noisy environments. It is enabled by setting bit 5 of the Modem Control Register (MCR) after configuring software flow control via EFR[3:0]. This is particularly valuable in industrial telemetry where corrupted Xon sequences could stall critical command-response loops.