Renesas 71321LA55TFG

Overview

71321LA55TFG 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 55 ns max read cycle time, 2V battery backup data retention, industrial temperature range (–40°C to +85°C), and operates on single 5V ±10% supply. Used in dual-CPU arbitration, shared memory buffers, and real-time control subsystems.

For engineers reviewing the 71321LA55TFG datasheet, 71321LA55TFG pinout, 71321LA55TFG application, or 71321LA55TFG equivalent, key selection criteria include its MASTER-only BUSY output capability, 55 ns timing grade, LA-series low-power standby (1 µA typical full standby), and 64-pin TQFP package compatibility with width-expansion architectures using IDT71421 SLAVE devices.

Technical Context

The 71321LA55TFG implements fully asynchronous dual-port access with independent left/right address, control, and I/O buses. Its on-chip arbitration logic uses chip enable (CEL/CER) and address match detection (A0–A10) to assert BUSYL/BUSYR outputs-open-drain signals requiring 270 Ω pull-ups-to block concurrent writes to identical addresses.

Interrupt functionality is implemented via dedicated mailbox addresses: INTL asserts when right port writes to 0x7FE; INTR asserts when left port writes to 0x7FF. Both flags are cleared by reading the respective address with OE enabled. The device supports battery backup mode at 2V with guaranteed data retention and consumes only 100 µA typical ICCDR.

Key Specifications

Pinout & Package

71321LA55TFG is housed in a 64-pin Thin Quad Flat Package (TQFP, code PNG64), measuring 14 mm × 14 mm × 1.4 mm, with exposed thermal pad (not electrically connected). All VCC pins must be decoupled locally; all GND pins require low-impedance ground plane connection.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT71421LA55TFG and CY7C1371BV33-55AC, the 71321LA55TFG uniquely delivers integrated MASTER arbitration, 55 ns timing at 5V, and 2V battery retention-making it irreplaceable for self-contained, low-power, industrial-grade dual-CPU shared memory where hardware-enforced determinism is required.

Availability

71321LA55TFG is available at Aetrix Electronics and suitable for industrial PLCs, automotive ADAS hubs, medical imaging pipelines, and avionics interfaces requiring stable component supply, long-term lifecycle support, and guaranteed industrial temperature performance.

Supply support for 71321LA55TFG 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 real-time embedded systems-delivering hardware arbitration, interrupt mailboxes, and battery-backed retention to eliminate software overhead in safety-critical dual-CPU architectures.

FAQ

What is the function of BUSYL and BUSYR on the 71321LA55TFG?

BUSYL and BUSYR are open-drain output flags on the 71321LA55TFG that signal write contention when both ports access the same memory address simultaneously. They require external 270 Ω pull-up resistors. When asserted (LOW), they inhibit writes on the respective port-this hardware arbitration eliminates race conditions without software intervention. As a MASTER device, 71321LA55TFG generates these signals; SLAVE devices like IDT71421 use them as inputs.

Does the 71321LA55TFG support battery backup operation, and what voltage is required?

Yes, the 71321LA55TFG supports battery backup operation with guaranteed data retention down to 2.0 V VCC (VDR = 2.0 V min). In this mode, it draws only 100 µA typical current (ICCDR), enabling direct connection to a CR2032 or similar coin cell. This feature ensures memory contents survive main power loss in industrial controllers, medical devices, and avionics systems-no external supervisor or power-fail circuitry is needed.

How do the interrupt flags INTL and INTR work on the 71321LA55TFG?

INTL and INTR are active-low open-drain interrupt outputs on the 71321LA55TFG. INTL asserts when the right port writes to address 0x7FE; INTR asserts when the left port writes to 0x7FF. Each flag is cleared by reading its respective address with OE enabled. These mailbox locations are standard SRAM cells-users store custom 8-bit messages. No external logic is required, enabling efficient event-driven interprocessor communication.

Can the 71321LA55TFG be used as a standalone dual-port RAM without a SLAVE device?

Yes, the 71321LA55TFG functions fully as a standalone 2K × 8 dual-port SRAM. Its MASTER arbitration logic, BUSY outputs, and interrupt flags operate independently. The SLAVE (IDT71421) is optional and only required when expanding data bus width beyond 8 bits-for example, combining one 71321LA55TFG MASTER with multiple IDT71421LA55TFG SLAVES to create a 16-bit or wider memory array with unified BUSY control.

What is the significance of the 'LA' suffix in 71321LA55TFG?

'LA' denotes the low-power version of the IDT71321, distinguishing it from the 'SA' (standard power) variant. The LA version delivers 1 µA typical full-standby current (ISB3), 200 µW typical battery backup consumption, and guaranteed 2V data retention-critical for energy-constrained or always-on applications. The 55 in 71321LA55TFG specifies the 55 ns maximum access speed grade, and TFG indicates the 64-pin TQFP (PNG64) package.