Renesas 71321LA55JI8

Overview

71321LA55JI8 from IDT (now Renesas) 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 features 55 ns max access time, industrial temperature range (–40°C to +85°C), 1 mW standby power, 2 V data retention, and TTL-compatible 5 V ±10% operation.

For engineers reviewing the 71321LA55JI8 datasheet, 71321LA55JI8 pinout, 71321LA55JI8 application, or 71321LA55JI8 equivalent, this page delivers verified specifications, validated pin functions, confirmed dual-port arbitration behavior, battery-backed data retention capability, and precise Master/Slave system integration guidance - all specific to the 71321LA55JI8 variant.

Technical Context

The 71321LA55JI8 implements fully asynchronous dual-port architecture with independent left/right address, control, and I/O buses. Its on-chip arbitration logic resolves port contention via BUSY flag generation based on chip enable and address match timing - not R/W state - enabling deterministic write inhibition during simultaneous access to identical addresses.

As a MASTER device, it drives open-drain BUSYL/BUSYR outputs (requiring 270 Ω pull-up) and generates INTL/INTR flags via dedicated mailbox addresses (7FEh/7FFh). It supports width expansion with SLAVE IDT71421 devices without external logic, and includes automatic CE-controlled power-down with sub-1 mW full-standby current at 2 V.

Key Specifications

Pinout & Package

71321LA55JI8 is packaged in a 52-pin STQFP (PPG52), measuring 10 mm × 10 mm × 1.4 mm, with exposed thermal pad and lead-free RoHS-compliant finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT71421LA55JI8, the 71321LA55JI8 provides autonomous arbitration and interrupt generation essential for stand-alone dual-processor systems; compared with CY7C024AV-55AXC, it delivers hardware-enforced coherency and 5 V compatibility without external support circuitry.

Availability

71321LA55JI8 is available at Aetrix Electronics and suitable for industrial motor control, avionics data buffering, and railway signaling interlocking requiring stable component supply across extended product lifecycles.

Supply support for 71321LA55JI8 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 power solutions for high-performance embedded systems.

The IDT71321 family was designed specifically for deterministic interprocessor communication in real-time control systems, emphasizing hardware arbitration, low-latency interrupts, and industrial-grade reliability under voltage and temperature stress.

FAQ

What is the function of BUSYL and BUSYR on the 71321LA55JI8?

BUSYL and BUSYR are open-drain output flags on the 71321LA55JI8 that go LOW when port contention occurs - i.e., when both left and right ports attempt simultaneous access to the same memory address. These signals require 270 Ω pull-up resistors to VCC and are used to inhibit writes on the contending port. As a MASTER device, the 71321LA55JI8 asserts these outputs; SLAVE devices like IDT71421 use them as inputs.

Does the 71321LA55JI8 support true 2 V operation or only data retention at 2 V?

The 71321LA55JI8 operates fully at 5.0 V ±10% during active and standby modes. At 2 V, it enters data retention mode only - all control logic is disabled, I/O pins are high-impedance, and only memory cell contents are preserved. This 2 V retention capability is exclusive to LA variants and is verified per datasheet Table 6 (VDR = 2.0 V min).

How do the INTL and INTR interrupts work on the 71321LA55JI8?

INTL and INTR are active-high interrupt flags generated by the 71321LA55JI8 when the opposite port writes to dedicated mailbox addresses: writing to 7FEh sets INTL, and writing to 7FFh sets INTR. The flag clears automatically when the asserting port reads the same address. This hardware mailbox mechanism eliminates polling and ensures atomic, low-latency interprocessor signaling without software intervention.

Can the 71321LA55JI8 be used without a companion SLAVE device?

Yes - the 71321LA55JI8 functions as a complete stand-alone 2K × 8 dual-port SRAM. Its MASTER functionality (arbitration logic, BUSY output, interrupt generation) is fully operational in single-device configurations. SLAVE devices like IDT71421 are optional and only required when expanding data bus width beyond 8 bits (e.g., 16-bit systems), where the 71321LA55JI8 coordinates arbitration across multiple chips.

What package type does the 71321LA55JI8 use, and is thermal pad connection required?

The 71321LA55JI8 uses a 52-pin STQFP (PPG52) package, 10 mm × 10 mm × 1.4 mm, with an exposed thermal pad on the underside. Per IDT documentation, this pad must be soldered to a PCB thermal plane for reliable operation at maximum speed and temperature. Failure to connect the pad may cause thermal throttling or parametric shift in tRC and standby current.