Diodes Incorporated PI7C9X794FCEX

Overview

PI7C9X794FCEX from Diodes Incorporated is a 1.62V–3.6V quad UART IC with 64-byte TX/RX FIFOs per channel, 5V-tolerant serial inputs, global interrupt output (INT#), and integrated IrDA 1.0/1.1 encoder/decoder. It supports up to 8 Mbps data rate with 64 MHz clock input and enables RS-485 half-duplex auto-direction control in industrial serial gateway applications.

For engineers reviewing the PI7C9X794FCEX datasheet, PI7C9X794FCEX pinout, PI7C9X794FCEX application, or PI7C9X794FCEX equivalent, key selection criteria include 4-channel independent 16C550 register compatibility, programmable FIFO trigger levels (1–60 bytes), Intel/Motorola bus interface select (16/68#), and hardware/software flow control support across all UARTs.

Technical Context

The PI7C9X794FCEX implements four independent UART channels sharing a single global interrupt source register and a unified 16-bit timer/counter. Each UART features a 16C550-compatible 5G register set, automatic RTS/CTS or DTR/DSR flow control with hysteresis, and IrDA 1.0/1.1 encoding/decoding with polarity-selectable RXD input.

It accepts crystal (up to 24 MHz) or external clock (up to 80 MHz) input via XTAL1/XTAL2, includes built-in power-on reset, and supports sleep mode with wake-up indication. The device uses an Intel/Motorola dual-mode parallel host interface controlled by the 16/68# pin, with address decoding (A7:A0) selecting UART channel (A4:A6), register offset (A0:A3), or global registers (A7).

Key Specifications

Pinout & Package

LQFP-64 package with exposed thermal pad; 10 mm × 10 mm body, 0.5 mm pitch, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XR16V794IL40-F, PI7C9X794FCEX offers extended temperature operation critical for industrial gateways; versus SC16IS752IPW, it delivers deterministic parallel-bus latency and native 5V tolerance essential for legacy serial infrastructure integration.

Availability

PI7C9X794FCEX is available at Aetrix Electronics and suitable for remote access servers, factory automation gateways, and point-of-sale terminals requiring stable component supply and long-term industrial lifecycle support.

Supply support for PI7C9X794FCEX 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 ICs for power management, signal integrity, and connectivity applications.

The PI7C9X794 belongs to Diodes' high-integration communications interface product line, designed specifically for bandwidth-constrained embedded systems needing multiple robust UART channels with minimal board space and software overhead.

FAQ

What bus interface modes does PI7C9X794FCEX support, and how is selection implemented?

The PI7C9X794FCEX supports both Intel and Motorola parallel bus interfaces. Selection is controlled by the 16/68# pin: HIGH configures IOR#, IOW#, and CS# for Intel timing, while LOW reassigns CS# as a combined read/write strobe and ties IOR# to VCC for Motorola operation. Address lines A7:A0 decode UART channel (A4:A6), register offset (A0:A3), or global registers (A7), ensuring full compatibility with legacy x86 and 68K-based designs without glue logic.

How does the PI7C9X794FCEX implement RS-485 half-duplex direction control?

The PI7C9X794FCEX provides hardware-assisted RS-485 direction control using RTS# or DTR# outputs. When enabled via FCTR bit-5 and MCR bit-2, the device automatically asserts RTS#/DTR# before transmission and de-asserts it after the final stop bit, eliminating timing-critical software delays. It also supports auto-address detection to suppress direction toggling during address-match frames, preventing bus contention in multi-drop networks without external logic or MCU intervention.

Can the FIFO trigger levels be configured differently for transmit and receive paths on the same UART channel?

Yes-each UART channel supports independent programming of TX and RX FIFO trigger levels via the Feature Control Register (FCTR) and FIFO Control Register (FCR). Valid levels include 1, 4, 8, 14, 16, 24, 28, 30, 56, or 60 bytes, selected through bit combinations in FCTR[7:6] and FCR[7:4]. This allows asymmetric buffering-for example, setting RX trigger to 14 bytes to minimize latency while using TX trigger of 24 bytes to maximize throughput efficiency under variable host write timing.

What is the role of the ENIR pin, and how does it affect UART initialization?

The ENIR pin (Pin 32) is a hardware enable for infrared mode, sampled at power-up, hardware reset (RST#), or software reset. When asserted HIGH, it forces all four UARTs to initialize in IrDA 1.0/1.1 mode, configuring TX/RX polarity, encoder/decoder circuitry, and pulse-shaping parameters automatically. This eliminates register writes for IR setup and ensures deterministic infrared readiness-critical for kiosk or medical devices requiring plug-and-play IR peripheral support without firmware dependency.