Diodes Incorporated PI7C9X798ME

Overview

PI7C9X798 from Diodes Incorporated is a high-integration octal UART IC supporting eight independent 16C550-compatible asynchronous serial channels, each with 64-byte TX/RX FIFOs, RS-485 half-duplex control, IrDA 1.0/1.1 encoding/decoding, and programmable 1–8 Mbps data rates using a 64 MHz external clock. It operates from 1.62V to 3.6V with 5V-tolerant modem inputs and targets multi-port serial interface cards in network management and factory automation.

For engineers reviewing the PI7C9X798 datasheet, PI7C9X798 pinout, PI7C9X798 application, or PI7C9X798 equivalent, key selection considerations include global interrupt handling across all 8 UARTs, simultaneous channel initialization, Intel/Motorola bus interface select via 16/68# pin, and hardware/software flow control configurability per channel.

Technical Context

The PI7C9X798 implements eight independent UART cores sharing a unified host interface (8-bit data bus, A[7:0] address decoding), global interrupt register, and a single 16-bit timer/counter. Each UART supports dual-mode flow control-hardware (RTS/CTS or DTR/DSR with hysteresis) and software (Xon/Xoff)-and includes dedicated registers for IrDA pulse inversion and RS-485 auto-address detection.

Its clock architecture accepts either a crystal (up to 24 MHz) or external clock (up to 80 MHz) on XTAL1/XTAL2, with internal prescaling enabling baud rates up to 8 Mbps (8× sampling) or 4 Mbps (16× sampling). The device integrates a power-on-reset circuit and supports sleep mode with wake-up indication via dedicated status bit.

Key Specifications

Pinout & Package

PI7C9X798 is housed in a 100-pin MQFP (Metric Quad Flat Package) with 0.5 mm pitch, thermally enhanced for industrial temperature operation and RoHS-compliant lead-free finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XR16V798, PI7C9X798 adds 5V-tolerant inputs and IrDA 1.1 for robust legacy integration and infrared debugging; versus XR17V358, it retains parallel bus compatibility essential for industrial add-in cards but trades PCIe convenience for broader hardware reuse.

Availability

PI7C9X798 is available at Aetrix Electronics and suitable for remote access servers, Ethernet-to-serial gateways, and network management cards requiring stable component supply, long-term industrial lifecycle support, and RoHS-compliant manufacturing.

Supply support for PI7C9X798 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 PI7C9X798 belongs to Diodes' high-density serial interface product line, engineered specifically for space-constrained multi-port communication systems demanding low-power operation, flexible bus interfacing, and robust ESD-hardened I/O.

FAQ

What bus interface modes does PI7C9X798 support, and how is selection implemented?

The PI7C9X798 supports both Intel-style (IOR#, IOW#, CS#) and Motorola-style (R/W#, CS# as combined strobe) parallel bus interfaces. Selection is controlled solely by the logic level on the 16/68# pin: HIGH enables Intel mode, LOW enables Motorola mode. No external logic or configuration registers are required-interface behavior changes automatically at power-up or reset based on this pin's sampled state.

How does the PI7C9X798 handle RS-485 half-duplex direction control without external transceivers?

The PI7C9X798 drives RS-485 direction control directly via its RTS# or DTR# outputs, configured through UART-specific MCR and FCTR bits. When enabled, the device asserts RTS# before transmitting and de-asserts it after the final stop bit, synchronized precisely with the UART shift register. This eliminates timing-critical external logic and supports auto-address detection for multi-drop networks.

Can the 64-byte FIFOs be used simultaneously across all 8 UARTs without performance degradation?

Yes-the PI7C9X798 allocates dedicated 64-byte TX and RX FIFO memory per UART channel, with independent read/write pointers and level counters. There is no shared FIFO resource or arbitration delay; each channel operates autonomously, enabling full 8-channel concurrency at up to 8 Mbps per port without FIFO overflow under typical interrupt service latencies.

What is the functional impact of the ENIR pin, and when must it be asserted?

The ENIR pin (active HIGH) configures all 8 UARTs to initialize in infrared mode at power-up or hardware reset. Its state is latched into MCR bit-6 of each UART, enabling IrDA 1.0/1.1 encoding/decoding and pulse inversion. If infrared operation is not required, ENIR may be tied LOW or left unconnected (pulled down internally); asserting it is mandatory only when IrDA PHY functionality is needed at boot.