Renesas 71321LA55TF

Overview

IDT71321LA55TF 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 cycle time, supports 5 V ±10% TTL-compatible operation, features battery-backed data retention down to 2 V, and operates across the industrial temperature range (–40°C to +85°C). It is used in dual-CPU arbitration systems requiring deterministic port-to-port handshaking.

For engineers reviewing the IDT71321LA55TF datasheet, IDT71321LA55TF pinout, IDT71321LA55TF application, or IDT71321LA55TF equivalent, key selection criteria include its master-mode BUSY arbitration, dual-interrupt flag behavior (INTL/INTR), 2V data retention capability, 52-pin STQFP package, and compatibility with IDT71421LA slave devices in width-expanded memory architectures.

Technical Context

The IDT71321LA55TF implements fully asynchronous dual-port access with independent left/right address, control, and I/O buses. Its on-chip arbitration logic monitors CE and address signals (A0–A10) to assert BUSYL/BUSYR outputs when simultaneous accesses to identical addresses occur - no external logic required.

Interrupt functionality uses dedicated mailbox addresses (7FE_H for INTL, 7FF_H for INTR) with edge-triggered flag assertion and software-clearable status. The LA variant enables ultra-low-power standby (1 mW typ.) and 2 V battery backup retention, distinguishing it from SA versions.

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, IDT71321LA55TF reduces system-level complexity by embedding arbitration and interrupts, while IDT71421LA55TF complements it in scalable memory width designs - neither offers standalone MASTER functionality or 2 V retention.

Availability

IDT71321LA55TF is available at Aetrix Electronics and suitable for real-time dual-CPU systems, industrial motion controllers, and battery-backed data loggers requiring stable component supply, long-term lifecycle assurance, and guaranteed industrial temperature performance.

Supply support for IDT71321LA55TF 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 communications and industrial markets.

IDT71321LA55TF belongs to IDT's legacy dual-port SRAM product line, engineered specifically for deterministic interprocessor communication in hard real-time embedded systems where hardware arbitration and low-power retention are critical.

FAQ

What is the function of BUSYL and BUSYR on the IDT71321LA55TF?

BUSYL and BUSYR are open-drain output flags indicating address contention between left and right ports. When both ports attempt to access the same memory location simultaneously, the IDT71321LA55TF asserts the corresponding BUSY signal low (requiring a 270 Ω pull-up) to inhibit writes on the delayed port. This hardware arbitration eliminates race conditions without software intervention or external logic.

Does the IDT71321LA55TF support true 2 V operation or only data retention at 2 V?

The IDT71321LA55TF supports active operation only at 5.0 V ±10%. Its 2 V specification applies solely to data retention mode: when VCC drops below 2 V, the device enters low-power hold and preserves memory contents using backup power - confirmed in Table 6 of the datasheet. Full read/write functionality requires nominal 5 V supply.

How do the interrupt mailboxes (7FE_H and 7FF_H) work in the IDT71321LA55TF?

Writing to address 7FE_H via the right port sets the INTL flag; writing to 7FF_H via the left port sets the INTR flag. Each flag is cleared by reading that same address with OE and CE asserted. These locations behave as standard SRAM cells - the data written becomes the message payload, enabling flexible interprocessor signaling beyond simple flagging.

Can the IDT71321LA55TF be used without the BUSY or interrupt features?

Yes. The IDT71321LA55TF operates as a standard dual-port SRAM when BUSY and interrupt pins are left unconnected or unused. Arbitration logic remains inactive unless both ports drive matching addresses with valid CE; interrupt flags remain unasserted unless mailbox addresses are accessed per Truth Table II. No configuration register or initialization is required to disable these features.

What is the difference between IDT71321LA55TF and IDT71321SA55TF?

The LA suffix denotes low-power retention capability: IDT71321LA55TF achieves 1 mW standby current and 2 V data retention, while IDT71321SA55TF consumes 5 mW standby and lacks battery backup support. Both share identical 55 ns timing, pinout, and functional logic - the LA variant is selected exclusively for applications requiring extended data hold during power loss.