Renesas CQ82C55A

Overview

CQ82C55A from Intersil is a CMOS Programmable Peripheral Interface IC designed for microprocessor-based I/O expansion, featuring 24 programmable I/O pins (Port A/B/C), three operational modes (Mode 0/1/2), direct bit set/reset on Port C, and full TTL compatibility across 0°C to +70°C. It delivers 2.5mA drive capability per I/O pin and supports high-speed, wait-state-free operation with 5MHz and 8MHz 80C86/80C88 systems.

For engineers reviewing the CQ82C55A datasheet, CQ82C55A pinout, CQ82C55A application, or CQ82C55A equivalent, this device serves as a drop-in CMOS replacement for the NMOS 8255A in legacy embedded control, industrial interface, and microcomputer peripheral subsystems requiring deterministic strobed or bidirectional bus I/O.

Technical Context

The CQ82C55A implements a static CMOS architecture with bus-hold circuitry on all I/O ports-eliminating external pull-ups-and integrates separate Group A (Port A + Port C upper) and Group B (Port B + Port C lower) control logic for independent mode configuration. Its control word register supports both write-only initialization and read-back of status bits (D7 = 1), enabling runtime verification of mode and interrupt enable states.

It provides hardware-level handshaking via dedicated Port C lines (e.g., STB, IBF, OBF, ACK, INTR) in Mode 1 and Mode 2, with interrupt enable flip-flops (INTE A/B) individually controllable via Port C bit set/reset commands-not standard port writes-ensuring precise peripheral interrupt management without disturbing other I/O states.

Key Specifications

Pinout & Package

Package: 44-lead MQFP (Pb-free), 10mm × 10mm body, Q44.10x10 drawing. RoHS-compliant matte tin termination, MSL Level 3 per J-STD-020.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar programmable peripheral interface applications.

Compared with CP82C55A-5Z and CS82C55A-5Z, the CQ82C55A offers optimized thermal dissipation and board-space efficiency in MQFP packaging for modern high-density embedded designs, while retaining full functional and timing equivalence with the 8255A family.

Availability

CQ82C55A is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, legacy microcomputer keyboard interfaces, test equipment digital pattern generation, and avionics data acquisition requiring stable component supply and long-term obsolescence mitigation.

Supply support for CQ82C55A 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

Intersil (now part of Renesas Electronics) is a semiconductor company specializing in high-performance analog and mixed-signal ICs for industrial, computing, and communications markets.

The 82C55A product line was engineered as a low-power, pin-compatible CMOS upgrade to the industry-standard 8255A, targeting microprocessor-based embedded systems where reliability, power efficiency, and backward compatibility are critical.

FAQ

What is the maximum operating frequency supported by the CQ82C55A?

The CQ82C55A supports wait-state-free operation with 5MHz and 8MHz 80C86 and 80C88 microprocessors, as verified in the FN2969 datasheet. Its timing parameters-including tRD, tWR, and tAW-are fully characterized for these clock domains, making the CQ82C55A suitable for high-throughput parallel I/O in legacy x86 embedded systems.

Does the CQ82C55A require external pull-up resistors on its I/O pins?

No, the CQ82C55A does not require external pull-up resistors due to integrated bus-hold circuitry on all I/O ports (PA, PB, PC). This feature maintains valid logic levels during tri-state conditions and eliminates the need for external biasing components, reducing BOM cost and PCB area-confirmed in the Functional Description section of the FN2969 datasheet for the CQ82C55A.

How is interrupt enable controlled on the CQ82C55A?

Interrupt enable (INTE) on the CQ82C55A is controlled exclusively via the Port C bit set/reset function-not standard port writes. INTE A is managed by setting/reseting PC4 (Mode 1) or PC6 (Mode 2), and INTE B by PC2. This ensures precise, non-destructive control of interrupt capability without altering other Port C output states, as defined in the Interrupt Control Functions section of the CQ82C55A datasheet.

Can the CQ82C55A be used as a direct replacement for the NMOS 8255A?

Yes, the CQ82C55A is explicitly specified as pin-compatible with the NMOS 8255A and functions as a drop-in CMOS replacement. It matches the 8255A's pinout, control protocol, and register map while adding bus-hold circuitry, lower power consumption (10µA standby), and enhanced drive strength (2.5mA), making the CQ82C55A ideal for upgrading legacy 8255A-based designs without hardware modification.

What are the valid operating temperature and package options for the CQ82C55A?

The CQ82C55A is rated for 0°C to +70°C operation and is supplied exclusively in a 44-lead MQFP (Pb-free) package per Q44.10x10 drawing. Unlike other variants such as CS82C55A-5Z (PLCC) or CP82C55A-5Z (PDIP), the CQ82C55A does not offer extended temperature or alternate package options-its specification is fixed to this commercial-grade MQFP configuration.