Renesas 71321LA25J8

Overview

71321LA25J8 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, 5 V ±10% TTL-compatible supply, industrial temperature range (–40°C to +85°C), and battery-backed data retention down to 2 V - enabling use in fault-tolerant controller memory buffers.

For engineers reviewing the 71321LA25J8 datasheet, 71321LA25J8 pinout, 71321LA25J8 application, or 71321LA25J8 equivalent, this page delivers verified timing parameters, port arbitration behavior, interrupt mailbox addressing (0x7FE/0x7FF), standby current (1 µA full standby), and PLCC-52 package mapping - all confirmed from IDT DSC-2691/17 (Sep 2019).

Technical Context

The 71321LA25J8 implements fully asynchronous dual-port operation with independent left/right address, control, and I/O buses. Its on-chip arbitration logic resolves contention via BUSY flag generation based solely on chip enable (CEL/CER) and address match (A0–A10), without requiring external logic.

As a MASTER-only device, it provides open-drain BUSYL/BUSYR outputs (requiring 270 Ω pull-ups) and two interrupt flags (INTL/INTR) tied to dedicated mailbox addresses (0x7FE and 0x7FF). It supports battery backup with 2 V data retention and consumes only 1 µA in full CMOS standby mode (ISB3).

Key Specifications

Pinout & Package

71321LA25J8 is packaged in 52-pin Plastic Leaded Chip Carrier (PLCC), body size ≈ 0.75 in × 0.75 in × 0.17 in, with lead finish matte tin and RoHS-compliant construction.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY7C1371BV33-167AXC and IDT71421LA25J8, the 71321LA25J8 uniquely integrates MASTER arbitration, dual interrupts, and 2 V retention in a 5 V industrial package - making it irreplaceable for legacy 5 V real-time control systems requiring hardware-coordinated dual-CPU memory access.

Availability

71321LA25J8 is available at Aetrix Electronics and suitable for motor control co-processors, redundant PLC modules, avionics display buffers, medical imaging pipelines, and industrial safety controllers requiring stable component supply across extended product lifecycles.

Supply support for 71321LA25J8 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 family was engineered specifically for deterministic interprocessor communication in real-time embedded systems - delivering hardware arbitration, interrupt mailboxes, and battery-backed dual-port SRAM in a single 5 V industrial package.

FAQ

What is the function of the BUSY pins on the 71321LA25J8?

The BUSYL and BUSYR pins on the 71321LA25J8 are open-drain outputs that assert low when address contention is detected between ports, signaling write inhibition to external logic or SLAVE devices. Per IDT DSC-2691/17, they require 270 Ω pull-up resistors and are active only in MASTER mode - unlike the SLAVE IDT71421 where BUSY pins are inputs. This behavior is intrinsic to the 71321LA25J8's on-chip arbitration logic.

Does the 71321LA25J8 support true 2 V operation or only data retention at 2 V?

The 71321LA25J8 supports full functional operation at 4.5–5.5 V, but only guarantees data retention (not active read/write) at 2.0 V, as specified in Table 06 of the datasheet. During retention mode, CE must be held high (>VCC − 0.2 V), and ICCDR is limited to 100–1500 µA. The 71321LA25J8 does not execute commands or respond to addresses at 2 V - it holds stored bits statically.

How are the interrupt flags INTL and INTR triggered and cleared on the 71321LA25J8?

INTL is asserted low when the right port writes to address 0x7FE; INTR is asserted low when the left port writes to 0x7FF. Both flags are cleared by reading the same address with OE and CE active (e.g., CEL=OEL=VIL for INTL). This mailbox mechanism is hardwired in the 71321LA25J8 and requires no configuration registers - confirmed in Truth Table II and Functional Description sections of DSC-2691/17.

Can the 71321LA25J8 operate as a SLAVE device in a MASTER/SLAVE configuration?

No - the 71321LA25J8 is exclusively a MASTER device. Its BUSY pins are outputs, and it contains on-chip arbitration logic. The SLAVE counterpart is the IDT71421LA25J8, which has BUSY pins as inputs and no arbitration circuitry. Attempting to use 71321LA25J8 as SLAVE violates its functional specification and will cause undefined BUSY behavior, as explicitly stated in Note 1 of the Functional Block Diagram and Pin Configurations.

What is the minimum required pull-up resistance for the INTL and INTR pins of the 71321LA25J8?

The INTL and INTR pins of the 71321LA25J8 are open-drain outputs and require external pull-up resistors. While the datasheet specifies 270 Ω for BUSY pins, it does not define a minimum value for INTL/INTR. However, per Figure 3 and AC Test Conditions, standard 1–10 kΩ pull-ups are used in reference designs to ensure fast rise times (<10 ns) under 30 pF load - consistent with TTL-compatible interfacing requirements for the 71321LA25J8.