Renesas 71321LA35TF

Overview

71321LA35TF 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 35 ns max read cycle time, 2V battery-backed data retention, industrial temperature operation (–40°C to +85°C), and supports fully asynchronous dual-port access with independent left/right control, address, and I/O buses.

For engineers reviewing the 71321LA35TF datasheet, 71321LA35TF pinout, 71321LA35TF application, or 71321LA35TF equivalent, key selection considerations include its MASTER-only arbitration logic, open-drain BUSYL/INTL outputs requiring 270Ω pull-ups, 1μA full-standby current at CMOS-level inputs, and compatibility with 16-bit-or-wider memory expansion using IDT71421 SLAVE devices.

Technical Context

The 71321LA35TF implements on-chip port arbitration based solely on chip enable (CEL/CER) and address match timing - not R/W state - enabling deterministic write-inhibit behavior during contention. Its BUSY output flags (BUSYL/BUSYR) are open-drain and require external 270Ω pull-up resistors; assertion occurs when both ports access identical addresses, with tBDD ≤ 35 ns (max) ensuring valid read data after BUSY deassertion.

Interrupt functionality uses dedicated mailbox addresses: INTL asserts on right-port write to 0x7FE, INTR on left-port write to 0x7FF; both flags clear via read-access to their respective addresses. The device operates exclusively from a single 5.0 V ±10% TTL-compatible supply and supports battery backup (2V) with 100–4000 µA retention current depending on grade.

Key Specifications

Pinout & Package

71321LA35TF is packaged in a 64-pin STQFP (PPG64), measuring 10 mm × 10 mm × 1.4 mm, with exposed thermal pad (not electrically connected). Pin functions are symmetric for left/right ports but differ for control logic (e.g., BUSYL is output, BUSYR is output; CER is input only on SLAVE).

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY7C1362BV33-167BZI and IDT71421LA35TF, the 71321LA35TF uniquely integrates MASTER arbitration, interrupt mailboxes, and 2V retention in a 5 V package - making it irreplaceable for deterministic, low-power, dual-processor shared-memory systems without external glue logic.

Availability

71321LA35TF is available at Aetrix Electronics and suitable for real-time industrial PLCs, avionics data loggers, medical imaging subsystems, and dual-core DSP co-processors requiring stable component supply across extended product lifecycles.

Supply support for 71321LA35TF 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 power management ICs for communications, computing, and industrial markets.

The IDT71321/71421 family was engineered specifically for deterministic interprocessor communication - delivering hardware-enforced arbitration, low-latency interrupts, and battery-backed SRAM in a single 5 V package for mission-critical embedded control.

FAQ

What is the function of the BUSYL and BUSYR pins on the 71321LA35TF?

The BUSYL and BUSYR pins on the 71321LA35TF are open-drain outputs that signal address contention between left and right ports. When both ports attempt to access the same memory location simultaneously, BUSYL and BUSYR go LOW (requiring 270Ω pull-up resistors) to inhibit writes on the losing port. This hardware arbitration eliminates the need for software semaphores and ensures deterministic behavior in real-time dual-processor systems using the 71321LA35TF.

Does the 71321LA35TF support true simultaneous read/write operations?

Yes - the 71321LA35TF supports fully asynchronous, simultaneous read and write operations to *different* memory addresses on its left and right ports. However, when both ports access the *same* address, the on-chip arbitration logic asserts BUSYL/BUSYR to block the write on the port whose enable/address signals arrive later (per tAPS timing). This behavior is intrinsic to the 71321LA35TF's MASTER architecture and guarantees data integrity without external logic.

How does the interrupt functionality work in the 71321LA35TF?

The 71321LA35TF implements hardware mailbox interrupts: writing to address 0x7FE (hex) via the right port sets the INTL flag, and writing to 0x7FF via the left port sets the INTR flag. Each flag clears automatically when the corresponding port reads its mailbox address. These open-drain signals require 270Ω pull-ups and provide sub-25 ns latency - enabling efficient, low-overhead inter-core signaling without polling. This interrupt mechanism is fixed and inherent to the 71321LA35TF design.

Can the 71321LA35TF operate with a 3.3 V supply?

No - the 71321LA35TF is specified exclusively for 5.0 V ±10% (4.5–5.5 V) operation and is TTL-compatible. Its internal circuitry, timing margins, and DC characteristics (e.g., VOL = 0.4 V, VIH = 2.2 V) are validated only within this range. Using 3.3 V will result in undefined behavior, failed arbitration, or permanent damage. For 3.3 V dual-port SRAM, consider alternatives like the Cypress CY7C1362BV33 series - but note those lack the integrated BUSY/interrupt logic of the 71321LA35TF.

What package type is used for the 71321LA35TF, and are there thermal considerations?

The 71321LA35TF uses a 64-pin STQFP (PPG64) package: 10 mm × 10 mm × 1.4 mm with an exposed thermal pad. Although the pad is not electrically connected, it must be soldered to a thermal land on the PCB for reliable operation at full industrial temperature (–40°C to +85°C) and to manage 325 mW typical active power dissipation. Four V_CC and four GND pins are provided - all must be individually routed to minimize ground bounce and ensure signal integrity in high-speed dual-port operation of the 71321LA35TF.