Renesas 71421SA55J8

Overview

71421SA55J8 from Integrated Device Technology (IDT) is a high-speed 2K × 8 dual-port static RAM configured as a SLAVE device in MASTER/SLAVE memory expansion systems, supporting fully asynchronous port-to-port access with BUSY input and interrupt flag (INTR) functionality. It delivers 55 ns maximum read cycle time, operates on single 5V ±10% supply, and targets industrial temperature range (–40°C to +85°C) for real-time interprocessor communication in embedded control subsystems.

For engineers reviewing the 71421SA55J8 datasheet, 71421SA55J8 pinout, 71421SA55J8 application, or 71421SA55J8 equivalent, this page provides verified technical context, validated pin functions, confirmed timing parameters for BUSY-driven arbitration and interrupt handling, and precise alternative part guidance for 16-bit-or-wider dual-port SRAM designs.

Technical Context

The 71421SA55J8 implements a dedicated SLAVE role in IDT's MASTER/SLAVE dual-port architecture: its BUSY pin is an input (not output), used to inhibit writes during address contention detected by the MASTER (IDT71321); it lacks on-chip arbitration logic but responds to external BUSY assertion with guaranteed tWB = 0 ns write-to-BUSY delay. It supports two independent asynchronous ports-left (L) and right (R)-each with separate CE, OE, R/W, address, and I/O lines, enabling concurrent read/write operations without internal synchronization overhead.

Interrupt functionality is implemented via dedicated mailbox addresses: INTR is asserted when the left port writes to address 7FF_H, and cleared when the right port reads/writes that same location; INTL is not generated by the 71421SA55J8 (only by MASTER). The device uses CMOS process technology, achieves 220 mA typical dynamic current at 55 ns speed grade, and enters low-power standby (ISB1 = 20 mA max) when both CER and CEL are high.

Key Specifications

Pinout & Package

71421SA55J8 is packaged in 64-pin STQFP (PPG64), measuring 10 mm × 10 mm × 1.4 mm, with exposed pad for thermal dissipation. Pin assignments conform to IDT's standard dual-port layout for TQFP/STQFP packages.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY7C1362BV33-55AXI and IDT71321SA55J8, the 71421SA55J8 uniquely delivers 5V-tolerant SLAVE functionality with zero-latency BUSY input response and dedicated interrupt mailbox - essential for minimizing component count and timing uncertainty in industrial dual-port memory systems.

Availability

71421SA55J8 is available at Aetrix Electronics and suitable for industrial PLC backplanes, avionics data concentrators, and medical imaging frame stores requiring stable component supply across extended product lifecycles.

Supply support for 71421SA55J8 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 IDT71421 family was designed specifically for high-reliability, asynchronous dual-port memory expansion in real-time embedded systems - prioritizing deterministic arbitration, low-latency interrupts, and industrial temperature robustness over density or voltage scaling.

FAQ

What is the role of 71421SA55J8 in a MASTER/SLAVE dual-port configuration?

The 71421SA55J8 functions exclusively as a SLAVE device: its BUSYR pin is an input that receives arbitration signals from a MASTER (e.g., IDT71321SA55J8) to inhibit writes during address contention. It does not generate BUSY outputs or perform arbitration itself - all decision logic resides in the MASTER. This division of labor simplifies system design and guarantees deterministic behavior in multi-chip memory banks.

Does 71421SA55J8 support battery backup or data retention at low voltage?

No. The 71421SA55J8 is an SA (Standard Active) variant and lacks battery backup capability. Only LA (Low-power Active) versions like IDT71421LA55J8 support 2V data retention. The 71421SA55J8 requires continuous 4.5–5.5V supply to maintain memory contents; loss of VCC results in immediate data loss.

How is the INTR interrupt flag used in 71421SA55J8?

The INTR flag is asserted (driven low) when the left port writes to memory address 7FF_H. It remains active until the right port accesses that same address (read or write). This mailbox mechanism enables hardware-triggered interprocessor communication without polling. Note: 71421SA55J8 does not generate INTL - that function is reserved for the MASTER device.

What package type is used for 71421SA55J8, and are there pin-compatible alternatives?

The 71421SA55J8 uses a 64-pin STQFP (PPG64) package with 10 mm × 10 mm body and 0.5 mm pitch. It is pin-compatible with other members of the IDT71421SA/LA family in the same package (e.g., 71421SA35J8), but not with PLCC or TQFP variants due to differing pinouts and thermal pad presence. Always verify land pattern against IDT's PPG64 mechanical drawing.

Can 71421SA55J8 operate as a standalone dual-port RAM without a MASTER device?

Yes - but with functional limitations. As a standalone device, 71421SA55J8 supports full dual-port read/write access, interrupt flag (INTR), and power-down modes. However, BUSYR must be held high (e.g., pulled up) since no MASTER is present to drive it. Arbitration and collision avoidance must then be handled in software or external logic, forfeiting the hardware advantage of the MASTER/SLAVE architecture.