Renesas 71321LA55PF

Overview

71321LA55PF 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 55 ns max read/write cycle time, 2V battery-backed data retention, industrial temperature operation (–40°C to +85°C), and supports fully asynchronous dual-port access. It is used in real-time embedded systems requiring concurrent CPU/DSP memory access without software arbitration.

For engineers reviewing the 71321LA55PF datasheet, 71321LA55PF pinout, 71321LA55PF application, or 71321LA55PF equivalent, this page provides verified technical context, validated pin functions, confirmed low-power standby behavior (1 µA full standby), and precise interrupt timing (tINS ≤ 45 ns) - all specific to the LA-grade 55 ns speed bin in 64-pin TQFP.

Technical Context

The 71321LA55PF implements on-chip port arbitration using address- and CE-based BUSY flag generation, with tAPS = 5 ns priority setup time ensuring deterministic conflict resolution. Its dual independent ports feature separate R/W, CE, OE, and 11-bit address buses (A0–A10), enabling true asynchronous read/write operations without external logic.

As a MASTER-only device, it drives open-drain BUSYL/BUSYR outputs (requiring 270 Ω pull-up) and generates INTL/INTR flags via dedicated mailbox addresses (7FEh/7FFh). The LA variant adds 2 V data retention capability and achieves 1 µA full-standby current (ISB3) under CMOS-level inputs, distinguishing it from SA versions.

Key Specifications

Pinout & Package

71321LA55PF is packaged in a 64-pin TQFP (PNG64), 14 mm × 14 mm × 1.4 mm body, lead-free and RoHS-compliant. 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 CY7C024AV-55AXC, 71321LA55PF integrates arbitration and interrupts, reducing BOM count and layout complexity; compared with IDT71421LA55PF, it provides autonomous MASTER functionality essential for standalone dual-processor designs.

Availability

71321LA55PF is available at Aetrix Electronics and suitable for industrial PLC backplanes, real-time motor control systems, and avionics data loggers requiring stable component supply, long-term lifecycle support, and guaranteed industrial temperature performance.

Supply support for 71321LA55PF 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.

The IDT71321 family was engineered specifically for deterministic interprocessor communication in resource-constrained embedded systems, emphasizing hardware arbitration, low-power retention, and seamless 5 V integration.

FAQ

What is the exact memory organization and bus width of the 71321LA55PF?

The 71321LA55PF contains 2K × 8 bits (2048 words × 8 bits) of static RAM, with two fully independent 8-bit bidirectional data buses (I/O0L–I/O7L and I/O0R–I/O7R), each supported by its own 11-bit address bus (A0L–A10L and A0R–A10R). This architecture enables true concurrent access without internal multiplexing. The 71321LA55PF does not support 16-bit word access natively - that requires pairing with a SLAVE device like IDT71421LA55PF.

Does the 71321LA55PF support battery backup, and what voltage is required?

Yes, the 71321LA55PF supports battery backup with guaranteed data retention at VCC = 2.0 V (minimum), as specified in Table 06 of the datasheet. This is a defining feature of the "LA" suffix variant. The device draws ≤1.5 mA (typical) in retention mode and maintains full data integrity without refresh. Note that retention is characterized at +25°C and is not production-tested, but guaranteed by design.

How does the BUSY arbitration logic work in the 71321LA55PF, and is external logic required?

The 71321LA55PF implements fully autonomous BUSY arbitration using on-chip logic that monitors address and chip-enable timing between ports. When both ports access the same address, the earlier port wins, and the later port's BUSY output (BUSYL or BUSYR) goes low after tBDD ≤ 50 ns (for 55 ns grade), blocking writes. No external logic is needed - the 71321LA55PF is self-contained as a MASTER device. External AND gates are only required if expanding beyond one MASTER/SLAVE pair.

What are the interrupt mailbox addresses for the 71321LA55PF, and how are they cleared?

The 71321LA55PF uses fixed SRAM addresses for hardware interrupts: writing to address 7FEh (hex) via the right port asserts the left-port INTL flag; writing to 7FFh (hex) via the left port asserts the right-port INTR flag. To clear INTL, the left port must perform a read or write to 7FEh with CEL = OEL = VIL; to clear INTR, the right port accesses 7FFh under the same control conditions. These are dedicated, user-accessible SRAM locations - no special registers or commands are involved.

Is the 71321LA55PF pin-compatible with faster or slower speed grades in the same family?

Yes, the 71321LA55PF is pin-compatible with other speed grades (e.g., 71321LA25PF, 71321LA35PF) and power variants (SA/LA) within the IDT71321 family, provided the same package (64-pin TQFP) is used. All share identical pinout, voltage levels, and functional behavior - only timing parameters differ. Swapping to a faster grade (e.g., 25 ns) requires no PCB changes but may demand tighter layout control for signal integrity.