Renesas 71421LA35PF8

Overview

71421LA35PF8 from Integrated Device Technology is a 2K × 8 dual-port static RAM configured as a SLAVE device in MASTER/SLAVE memory expansion systems, supporting fully asynchronous port-to-port communication with BUSY input and interrupt flags (INTL/INTR), 35 ns max read cycle time, 2V battery-backed data retention, and industrial temperature operation (–40°C to +85°C) - used in real-time interprocessor messaging and redundant control subsystems.

For engineers reviewing the 71421LA35PF8 datasheet, 71421LA35PF8 pinout, 71421LA35PF8 application, or 71421LA35PF8 equivalent, this page delivers verified electrical specs, validated SLAVE-side BUSY/INT timing, confirmed 64-pin TQFP package mapping, and precise functional distinctions from MASTER IDT71321 devices.

Technical Context

The 71421LA35PF8 implements a dedicated SLAVE role in dual-port SRAM architectures: its BUSY pin is an input (not output), enabling write-inhibit arbitration when driven low by a MASTER IDT71321; it lacks on-chip arbitration logic and relies entirely on external BUSY assertion for contention resolution. It supports independent left/right port access with separate CE/OE/R/W controls and full 2K × 8 address space visibility per port.

Interrupt functionality is implemented via two mailbox addresses: writing to 7FE_H on the right port sets INTL, and writing to 7FF_H on the left port sets INTR; clearing requires reading those same addresses with OE active. Battery backup operates at 2V with ≤100 µA typical retention current, validated only for LA-grade parts.

Key Specifications

Pinout & Package

71421LA35PF8 is packaged in a 64-pin TQFP (PNG64) with 0.5 mm pitch, 14 mm × 14 mm body, and exposed thermal pad. Pin functions are symmetric across left/right ports with dedicated BUSY input and interrupt outputs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT71421SA35PF8, the 71421LA35PF8 adds critical 2V retention for safety-critical holdover, while CY7C1371BV33-167BZC replaces asynchronous dual-port semantics with QDR protocol - making it incompatible for BUSY-based arbitration or mailbox-style interrupts.

Availability

71421LA35PF8 is available at Aetrix Electronics and suitable for real-time interprocessor messaging, redundant control subsystems, avionics data buffering, and industrial PLC I/O mapping requiring stable component supply across extended product lifecycles.

Supply support for 71421LA35PF8 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.

The IDT71421 family was designed specifically for high-reliability dual-processor systems requiring hardware-arbitrated shared memory, with the LA variant optimized for battery-backed industrial control and aerospace applications.

FAQ

What is the role of 71421LA35PF8 in a MASTER/SLAVE dual-port SRAM configuration?

The 71421LA35PF8 serves exclusively as a SLAVE device: its BUSY pins (BUSYL/BUSYR) are inputs that accept write-inhibit signals from a MASTER IDT71321, and it lacks internal arbitration logic. It cannot operate standalone as a MASTER. This strict functional partitioning ensures deterministic contention resolution in width-expanded memory systems - a core design requirement validated in the 71421LA35PF8 datasheet.

Does 71421LA35PF8 support battery backup, and what voltage is required?

Yes, the 71421LA35PF8 supports battery-backed data retention at exactly 2.0 V (VDR), with typical ICCDR of 100 µA and maximum 1500 µA under commercial conditions. This is a defining feature of the "LA" suffix and is not present in SA variants. The 2V threshold is specified in Table 6 of the datasheet and is guaranteed - not typical - for data retention.

How do the interrupt flags INTL and INTR function on 71421LA35PF8?

INTL is asserted when the right port writes to address 7FE_H; INTR is asserted when the left port writes to 7FF_H. Both are open-drain outputs requiring 270 Ω pull-ups. Clearing occurs by reading those addresses with OE active - no dedicated reset command. This mailbox mechanism is identical across all IDT71421LA variants and is electrically verified in Truth Table II.

What package type and pin count does 71421LA35PF8 use?

The 71421LA35PF8 uses a 64-pin TQFP (PNG64) package with 0.5 mm pitch and 14 mm × 14 mm body size, as confirmed in the Pin Configurations section (page 2, Figure 3) of the datasheet. It is distinct from the 52-pin PLCC/STQFP variants and shares pinout compatibility with other 64-pin IDT71421X35PF8 variants.

Can 71421LA35PF8 be used without a MASTER IDT71321 device?

Yes - but only in non-contention scenarios. When BUSYL and BUSYR are held high (e.g., tied to VCC via 270 Ω pull-ups), the 71421LA35PF8 operates as a standard dual-port SRAM with independent left/right access. However, hardware arbitration and automatic write-inhibit during address collisions require connection to a MASTER IDT71321 - a dependency explicitly defined in the Functional Description (page 16).