Renesas 71321LA25TFI

Overview

IDT71321LA25TFI 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 features 25 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 IDT71321LA25TFI datasheet, IDT71321LA25TFI pinout, IDT71321LA25TFI application, or IDT71321LA25TFI equivalent, key selection considerations include dual-port asynchronous read/write timing, MASTER-side BUSY output behavior, interrupt mailbox addressing (7FEh/7FFh), and low-power battery backup capability - all critical for deterministic multi-CPU memory sharing.

Technical Context

The IDT71321LA25TFI implements fully independent left/right ports with separate address, control, and I/O buses, enabling true concurrent access without software coordination. Its on-chip arbitration logic resolves port contention via BUSY flag assertion based on chip enable and address match timing - not R/W state - ensuring 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 resistors, while generating INTL/INTR flags via dedicated mailbox writes (7FEh for left interrupt set, 7FFh for right). The LA variant supports 2 V data retention with ≤100 µA ICCDR, distinguishing it from SA versions.

Key Specifications

Pinout & Package

Package: 64-pin TQFP (PNG64), 14 mm × 14 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-25AXC and NVTFS256K8, IDT71321LA25TFI uniquely delivers integrated hardware arbitration, interrupt mailboxes, and 2 V battery retention in a 2K × 8 dual-port form factor - making it irreplaceable for deterministic, low-latency, power-conscious interprocessor memory sharing.

Availability

IDT71321LA25TFI is available at Aetrix Electronics and suitable for industrial PLC backplanes, aerospace flight control units, and battery-backed data loggers requiring stable component supply across extended product lifecycles.

Supply support for IDT71321LA25TFI 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 computing and communications infrastructure.

IDT71321LA25TFI 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-power retention are mandatory.

FAQ

What is the function of BUSYL and BUSYR on the IDT71321LA25TFI?

BUSYL and BUSYR are open-drain output flags on the IDT71321LA25TFI that indicate port contention when both left and right ports attempt simultaneous access to the same memory address. They require external 270 Ω pull-up resistors to VCC and assert LOW to inhibit writes on the contending port. This hardware arbitration eliminates race conditions without software intervention.

Does the IDT71321LA25TFI support true simultaneous read/write operations?

Yes - the IDT71321LA25TFI supports fully asynchronous, independent read and write operations on left and right ports. One port can read from address 010h while the other writes to address 3F0h, with no timing dependency between them. Only identical address access triggers BUSY arbitration.

How does interrupt generation work in the IDT71321LA25TFI?

The IDT71321LA25TFI uses dedicated SRAM locations: writing to 7FEh (hex) via the right port sets the INTL flag, and writing to 7FFh via the left port sets the INTR flag. Each flag remains asserted until cleared by a read access to its respective address with OE and CE active - enabling hardware-synchronized message passing.

What is the significance of the 'LA' suffix in IDT71321LA25TFI?

The 'LA' denotes the low-power, battery-retentive variant of the IDT71321. It guarantees data retention down to 2.0 V supply voltage with ≤100 µA retention current, unlike the 'SA' (standard access) version. This makes IDT71321LA25TFI suitable for systems requiring non-volatile memory hold during main power interruption.

Can the IDT71321LA25TFI be used without external pull-up resistors on BUSY pins?

No - BUSYL and BUSYR are open-drain outputs per datasheet Note 1 and Figure 3. Without 270 Ω pull-up resistors to VCC, these signals cannot drive HIGH and will remain floating or LOW, causing permanent write inhibition on contending ports and breaking arbitration functionality.