Renesas 71321LA55J

Overview

IDT71321LA55J from Integrated Device Technology (IDT) is a high-speed 2K × 8 dual-port static RAM with interrupt and BUSY arbitration logic, designed as a MASTER device for interprocessor communication in real-time embedded systems. It delivers 55 ns max read/write cycle time, supports industrial temperature range (–40°C to +85°C), operates on single 5V ±10% supply, and enables battery-backed data retention at 2V - used in dual-CPU arbitration buffers and shared-memory co-processor interfaces.

For engineers reviewing the IDT71321LA55J datasheet, IDT71321LA55J pinout, IDT71321LA55J application, or IDT71321LA55J equivalent, key selection considerations include its MASTER-only BUSY output architecture, 2V data retention capability (LA variant), 52-pin STQFP package compatibility, and interrupt mailbox addressing at 7FEh/7FFh - critical for deterministic inter-core messaging in avionics and industrial PLCs.

Technical Context

The IDT71321LA55J implements fully asynchronous dual-port access with independent left/right address, control, and I/O buses. Its on-chip arbitration logic uses chip-enable and address-match timing (tAPS = 5 ns min) to assert open-drain BUSYL/BUSYR outputs - no external logic required for width expansion with slave devices like IDT71421.

Interrupt functionality relies on dedicated mailbox addresses: INTL asserts when right port writes to 7FEh; INTR asserts when left port writes to 7FFh. Both flags are cleared by reading the same address with OE enabled - enabling lock-free message passing without software polling overhead.

Key Specifications

Pinout & Package

Package: 52-pin STQFP (PPG52), 10 mm × 10 mm × 1.4 mm body, lead-free and RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-port SRAM applications.

Compared with CY7C024AV-55AXC and R1EX24002AS0C-55#U0, IDT71321LA55J uniquely integrates MASTER arbitration, interrupt mailboxes, and 2V data retention in a single 52-pin STQFP - reducing BOM count, PCB area, and firmware complexity in safety-critical dual-processor systems.

Availability

IDT71321LA55J is available at Aetrix Electronics and suitable for avionics flight control buffers, industrial PLC dual-core messaging, and automotive ADAS sensor fusion hubs requiring stable component supply across extended temperature and long product lifecycles.

Supply support for IDT71321LA55J 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

Integrated Device Technology (IDT), now part of Renesas Electronics, is a fabless semiconductor company specializing in timing, memory interface, and RF solutions for high-performance computing and communications infrastructure.

IDT71321LA55J belongs to IDT's legacy dual-port SRAM product line, engineered specifically for deterministic interprocessor communication in real-time embedded systems where hardware arbitration and low-latency messaging are essential.

FAQ

What is the function of BUSYL and BUSYR on IDT71321LA55J?

BUSYL and BUSYR are open-drain output flags on IDT71321LA55J that indicate write contention when both ports access the same memory location. They require 270 Ω pull-up resistors and drive low to inhibit writes on the contending port - enabling hardware-level arbitration without external logic. This behavior is exclusive to the MASTER IDT71321LA55J; SLAVE devices like IDT71421 use these pins as inputs.

Does IDT71321LA55J support battery backup operation?

Yes, IDT71321LA55J supports battery backup operation with guaranteed data retention down to 2.0 V (VDR), as specified in Table 06 of the datasheet. In this mode, ICCDR is ≤1500 µA (commercial) or ≤4000 µA (industrial), allowing extended retention from a coin-cell battery during main power loss - a feature exclusive to LA variants like IDT71321LA55J.

How do the interrupt mailboxes work on IDT71321LA55J?

IDT71321LA55J uses address 7FEh to trigger INTL (left port interrupt) when written by the right port, and 7FFh to trigger INTR (right port interrupt) when written by the left port. Each flag is cleared by reading the same address with OE enabled. This hardware mailbox mechanism enables lock-free, low-latency interprocessor signaling with ≤25 ns interrupt set time (tINS) - eliminating polling overhead in real-time systems.

What package type is used for IDT71321LA55J?

IDT71321LA55J is packaged in a 52-pin STQFP (PPG52) with 10 mm × 10 mm × 1.4 mm dimensions. This surface-mount package features gull-wing leads, RoHS compliance, and thermal performance validated for industrial temperature operation. Pin configuration matches Figure 3a in the datasheet, with dedicated VCC/GND pairs distributed for noise immunity.

Can IDT71321LA55J be used with IDT71421 devices in a MASTER/SLAVE configuration?

Yes, IDT71321LA55J is explicitly designed as the MASTER in MASTER/SLAVE configurations with IDT71421 SLAVE devices. The IDT71321LA55J's BUSY outputs connect directly to IDT71421's BUSY inputs to enforce write arbitration across expanded 16-bit-or-wider memory systems - enabling full-speed, error-free operation without additional discrete logic per the functional description on page 2 of the datasheet.