Renesas 71321LA25TF8

Overview

IDT71321LA25TF8 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 in real-time embedded systems. It delivers 25 ns max access time, 1 mW standby power (LA version), 2 V data retention, and operates on single 5V ±10% supply across –40°C to +85°C industrial temperature range.

For engineers reviewing the IDT71321LA25TF8 datasheet, IDT71321LA25TF8 pinout, IDT71321LA25TF8 application, or IDT71321LA25TF8 equivalent, key selection considerations include port-to-port arbitration timing (tBAA/tBDA ≤20 ns), interrupt mailbox addressing (7FEH/7FFH), open-drain BUSY output requiring 270 Ω pull-up, and compatibility with IDT71421SLAVE devices in 16-bit+ memory expansion.

Technical Context

The IDT71321LA25TF8 implements fully asynchronous dual-port architecture with independent left/right address, control, and I/O buses. Its on-chip arbitration logic resolves contention via BUSY flag generation based on chip enable and address match detection - not R/W state - ensuring deterministic write inhibition during simultaneous access to identical addresses.

Interrupt functionality uses dedicated SRAM mailboxes (7FEH for INTL, 7FFH for INTR) with hardware-set/clear semantics: right-port write to 7FFH asserts INTR; left-port read/write to 7FEH clears INTL. Both ports support TTL-compatible signaling and automatic power-down when CE = VIH.

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 CY7C1371DV33 and IDT71421LA25TF8, the IDT71321LA25TF8 uniquely integrates MASTER arbitration, dual interrupt mailboxes, and 2V data retention in a single 5V industrial-grade package - eliminating external components required by alternatives.

Availability

IDT71321LA25TF8 is available at Aetrix Electronics and suitable for real-time motion control, telecom packet buffering, and automotive ADAS sensor fusion requiring stable component supply over extended production lifecycles.

Supply support for IDT71321LA25TF8 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 solutions for communications and computing infrastructure.

IDT71321LA25TF8 belongs to IDT's dual-port SRAM product line, engineered specifically for deterministic interprocessor communication in hard real-time embedded systems where software-based synchronization introduces unacceptable latency.

FAQ

What is the function of the BUSY pin on IDT71321LA25TF8?

The BUSY pin on IDT71321LA25TF8 is an open-drain output that signals port contention. When both ports attempt simultaneous access to the same memory address, the IDT71321LA25TF8 asserts BUSY LOW to inhibit writes on the later-arriving port. This hardware arbitration eliminates the need for software semaphores and ensures deterministic behavior in multi-CPU systems.

Does IDT71321LA25TF8 support battery backup operation?

Yes, IDT71321LA25TF8 supports battery backup operation with guaranteed data retention at VCC ≥ 2.0 V. This LA-series feature allows the device to maintain memory contents during main power loss, making it suitable for applications requiring crash-robust state preservation such as automotive event loggers and industrial safety controllers.

How do the interrupt mailboxes work in IDT71321LA25TF8?

IDT71321LA25TF8 uses two dedicated SRAM locations as hardware-managed mailboxes: address 7FEH controls INTL (left-port interrupt), and 7FFH controls INTR (right-port interrupt). A write to 7FFH by the left port sets INTR; a read or write to 7FEH by the right port clears INTL. These operations occur without CPU intervention, enabling zero-latency interprocessor signaling.

Can IDT71321LA25TF8 be used without external pull-up resistors on BUSY and INT pins?

No, IDT71321LA25TF8 requires external 270 Ω pull-up resistors on BUSY and INT pins because they are open-drain outputs. Without pull-ups, these signals cannot drive HIGH, causing failure of arbitration and interrupt functionality. The datasheet explicitly specifies this requirement in Note 2 of the Functional Block Diagram.

What is the difference between IDT71321LA25TF8 and IDT71421LA25TF8?

IDT71321LA25TF8 is the MASTER device with on-chip arbitration logic, BUSY output, and INTL/INTR flags; IDT71421LA25TF8 is the SLAVE device with BUSY input only and no arbitration logic. They are designed to operate together in width-expanded memory systems, but IDT71321LA25TF8 can function standalone while IDT71421LA25TF8 cannot.