Renesas 71421LA55J

Overview

IDT71421LA55J from Integrated Device Technology is a high-speed 2K × 8 dual-port static RAM configured as a SLAVE device in MASTER/SLAVE memory expansion systems, supporting asynchronous port-to-port communication with BUSY input and interrupt flag (INTR) functionality. It delivers 55 ns max read cycle time, 2 V data retention capability, 1 µA full-standby current (ISB3), and operates across –40°C to +85°C industrial temperature range on single 5 V ±10% supply - used in real-time interprocessor messaging and shared-memory arbitration circuits.

For engineers reviewing the IDT71421LA55J datasheet, IDT71421LA55J pinout, IDT71421LA55J application, or IDT71421LA55J equivalent, key selection criteria include its role as SLAVE in width-expanded dual-port SRAM systems, BUSY input behavior, interrupt mailbox addressing (7FF_H), battery backup support, and compatibility with IDT71321 MASTER devices for 16-bit+ word-width implementations.

Technical Context

The IDT71421LA55J implements dedicated SLAVE-side arbitration logic: BUSYR is an input that inhibits writes when asserted low, while INTR is an open-drain output flag set by left-port writes to address 7FF_H. It lacks on-chip arbitration control or BUSY output - those functions reside solely in the MASTER IDT71321.

Its timing architecture supports CE-controlled and R/W-controlled write cycles, with tWC = 55 ns, tWP = 30 ns, and port-to-port delays including tWDD ≤ 80 ns and tDDD ≤ 55 ns. Data retention at 2 V is guaranteed, with ICCDR ≤ 4000 µA under industrial conditions.

Key Specifications

Pinout & Package

Package: 64-pin STQFP (PPG64), 10 mm × 10 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 CY7C024AV-55JC, IDT71421LA55J reduces system-level complexity by integrating SLAVE-specific BUSY input and interrupt mailbox logic; compared with IDT71321LA55J, it eliminates redundant arbitration circuitry when deployed as secondary port in asymmetric dual-CPU topologies.

Availability

IDT71421LA55J is available at Aetrix Electronics and suitable for industrial motion control, avionics redundancy modules, and telecom baseband processing requiring stable component supply, long-lifecycle support, and guaranteed -40°C to +85°C operation.

Supply support for IDT71421LA55J 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, designs high-performance timing, memory, and interface solutions for communications, computing, and industrial markets.

IDT71421LA55J belongs to the IDT71321/71421 dual-port SRAM family, engineered specifically for hardware-synchronized interprocessor communication in real-time embedded systems where deterministic latency and data coherency are critical.

FAQ

What is the function of BUSYR on the IDT71421LA55J?

BUSYR is an input-only signal on the IDT71421LA55J. When driven low by a MASTER device (e.g., IDT71321LA55J), it internally inhibits write operations to the right port regardless of R/WR or CER state. It must be externally pulled high (270 Ω) when not connected to a MASTER. The IDT71421LA55J does not generate BUSY signals - only consumes them.

How does interrupt generation work on the IDT71421LA55J?

The IDT71421LA55J asserts its open-drain INTR output when the left port writes to memory address 7FF_H (hex), per Truth Table II. This write must meet timing: CER = VIH, CEL = R/WL = VIL. To clear INTR, the right port reads or writes 7FF_H with CER = OER = VIL. The IDT71421LA55J does not support INTL - that flag is exclusive to the left port of MASTER devices.

Can IDT71421LA55J operate without a MASTER device?

Yes - the IDT71421LA55J functions as a standalone 2K × 8 dual-port SRAM without a MASTER. BUSYR must be held high (e.g., via 270 Ω pull-up) to enable normal write operations. All timing, interrupt, and retention specifications remain valid. However, hardware arbitration and automatic width expansion require pairing with IDT71321LA55J.

What is the significance of the 'LA' suffix in IDT71421LA55J?

The 'LA' denotes Low-power Active/Standby variant: it achieves 1 µA full-standby current (ISB3) and guaranteed 2 V data retention - unlike 'SA' versions which specify 5 mW typical standby and no retention guarantee. The 'LA' suffix also correlates with tighter ISB1/ISB2/ISB4 current limits across commercial and industrial grades, confirmed in DC Electrical Characteristics Tables 04a/b.

Which package variants are available for IDT71421LA55J?

IDT71421LA55J is offered in 64-pin STQFP (PPG64) per the datasheet's Pin Configuration diagrams and Ordering Information. While the family supports PLCC, STQFP, and TQFP options, the 'J' suffix in IDT71421LA55J specifically denotes the PPG64 package - verified by footprint dimensions (10 mm × 10 mm × 1.4 mm) and pin count consistency across Figures 03 and 03a.