Renesas 71321LA45J

Overview

71321LA45J from Integrated Device Technology is a high-speed 2K × 8 dual-port static RAM with interrupt and BUSY arbitration logic, designed as a MASTER device for interprocessor communication. It delivers 45 ns max read/write cycle time, supports 5 V ±10% TTL-compatible operation, enables battery-backed data retention at 2 V, and operates across –40°C to +85°C industrial temperature range - used in real-time embedded control systems requiring concurrent memory access.

For engineers reviewing the 71321LA45J datasheet, 71321LA45J pinout, 71321LA45J application, or 71321LA45J equivalent, key selection criteria include its master-mode BUSY arbitration, dual-interrupt flag support (INTL/INTR), low 1 µA full-standby current, 52-pin PLCC package compatibility, and verified interoperability with IDT71421LA slave devices in 16-bit+ memory expansion.

Technical Context

The 71321LA45J 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 output assertion based on chip enable (CEL/CER) and address match timing - not R/W state - ensuring deterministic write inhibition during simultaneous access to identical addresses.

Interrupt functionality uses dedicated mailbox addresses (7FE_H for INTL, 7FF_H for INTR) with set/clear semantics defined by port-specific write patterns. The device features open-drain BUSY/INT outputs requiring 270 Ω pull-up resistors and supports battery backup with guaranteed 2 V data retention - a capability exclusive to LA-grade variants.

Key Specifications

Pinout & Package

71321LA45J is housed in a 52-pin Plastic Leaded Chip Carrier (PLCC, package code PLG52) with 0.050" lead pitch and .75" × .75" body size. Pin 1 is located at the index corner adjacent to the notch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT71421LA45J, the 71321LA45J provides autonomous master arbitration and interrupt generation - enabling standalone dual-processor designs. Versus CY7C1371BV33-100AXC, it retains 5 V compatibility, deterministic contention resolution, and battery retention - critical for industrial control lifecycles exceeding 15 years.

Availability

71321LA45J is available at Aetrix Electronics and suitable for real-time motion control, dual-core processor interfacing, industrial PLC I/O mapping, and avionics data concentrator applications requiring stable component supply over extended production lifecycles.

Supply support for 71321LA45J 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, RF, and sensor signal conditioning ICs for communications, computing, and industrial markets.

The IDT71321/71421 family was engineered specifically for deterministic interprocessor communication in hard real-time systems - prioritizing hardware arbitration, low-latency interrupts, and robust data retention over raw bandwidth.

FAQ

What is the function of the BUSY pin on the 71321LA45J?

The BUSY pin on the 71321LA45J is an open-drain output that asserts low when port contention occurs - i.e., when both left and right ports attempt to access the same memory address simultaneously. As a MASTER device, 71321LA45J uses BUSY to inhibit writes on the losing port, ensuring data integrity without software intervention. External 270 Ω pull-up required per datasheet DSC-2691/17.

Does the 71321LA45J support battery backup operation?

Yes, the 71321LA45J supports battery backup operation with guaranteed data retention down to 2 V supply voltage. This LA-grade feature enables seamless hold-mode operation during main power failure - critical for industrial controllers and avionics. Retention current is specified at ≤1500 µA (commercial) or ≤4000 µA (industrial) at 2 V, per Table 6 in datasheet DSC-2691/17.

How does interrupt handling work in the 71321LA45J?

The 71321LA45J implements hardware interrupts using fixed mailbox addresses: writing to 7FE_H sets INTL (left port flag), and writing to 7FF_H sets INTR (right port flag). Clearing is performed by reading those same addresses. This enables zero-overhead interprocessor signaling - for example, a DSP can assert INTR to notify an MCU of completed FFT processing without polling or shared registers.

Can the 71321LA45J be used without a companion SLAVE device?

Yes, the 71321LA45J functions as a complete standalone 8-bit dual-port SRAM. Its MASTER arbitration logic remains active but only affects internal port contention - no external SLAVE is required. The device is commonly deployed alone in applications like dual-CPU debug monitors or FPGA-CPU co-processing buffers where 8-bit width suffices and deterministic arbitration is needed.

What package type is used for the 71321LA45J?

The 71321LA45J is supplied in a 52-pin Plastic Leaded Chip Carrier (PLCC) package, designated PLG52 per IDT documentation. This package features a .75" × .75" body, J-lead geometry, and is compatible with standard surface-mount reflow profiles and socket-based prototyping - confirmed in Pin Configuration diagrams (DSC-2691/17, pages 2–3).