Renesas 71421LA20JG

Overview

71421LA20JG from Integrated Device Technology (IDT) 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). It delivers 20 ns read cycle time, 2 V data retention, 1 µA full-standby current (CMOS-level inputs), and operates on a single 5V ±10% supply across –40°C to +85°C industrial temperature range. It is used in real-time interprocessor communication buffers where deterministic arbitration and low-power battery backup are required.

For engineers reviewing the 71421LA20JG datasheet, 71421LA20JG pinout, 71421LA20JG application, or 71421LA20JG equivalent, key selection criteria include SLAVE-side BUSY input timing (tWB = 0 ns), interrupt mailbox address mapping (7FEH/7FFH), 64-pin TQFP package compatibility, and verified 2 V data retention behavior under battery backup conditions.

Technical Context

The 71421LA20JG implements a dedicated SLAVE role in dual-port SRAM systems: its BUSY pin functions exclusively as an input to inhibit writes during contention, unlike the MASTER IDT71321 which drives BUSY as an open-drain output. It lacks on-chip arbitration logic and relies entirely on external BUSY assertion from a MASTER device.

Interrupt functionality is implemented via two fixed-address mailboxes - writing to 7FEH sets INTL, writing to 7FFH sets INTR - with no internal arbitration between interrupt sources. All timing parameters (tINS = 20 ns max, tINR = 20 ns max) are specified relative to CE/R/W transitions and apply identically to both ports.

Key Specifications

Pinout & Package

71421LA20JG 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 for left/right ports, with dedicated control, address, I/O, and interrupt/BUSY terminals.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY7C024AV-20AXC, 71421LA20JG reduces design complexity by embedding BUSY-driven write inhibition and interrupt mailboxes; compared with IDT71321LA20JG, it trades arbitration capability for lower cost and optimized SLAVE-side timing - ideal for fixed-role slave nodes in deterministic real-time systems.

Availability

71421LA20JG is available at Aetrix Electronics and suitable for industrial control systems, avionics data loggers, and medical device configuration storage requiring stable component supply, long-term lifecycle support, and guaranteed 2 V data retention behavior.

Supply support for 71421LA20JG 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.

The IDT71321/71421 family was engineered specifically for deterministic, low-latency interprocessor communication in real-time embedded systems - emphasizing hardware arbitration, interrupt signaling, and battery-backed data integrity over raw density or speed.

FAQ

What is the role of 71421LA20JG in a MASTER/SLAVE dual-port SRAM configuration?

The 71421LA20JG functions exclusively as a SLAVE device: its BUSY pin is an input that inhibits writes when asserted by a MASTER (e.g., IDT71321LA20JG), and it lacks on-chip arbitration logic. It relies on external BUSY signaling for contention resolution and supports interrupt mailboxes at addresses 7FEH and 7FFH. This role simplifies system design by offloading arbitration to the MASTER while maintaining full 2K × 8 memory access on both ports.

Does 71421LA20JG support true nonvolatile operation, or only data retention?

The 71421LA20JG supports data retention - not full nonvolatility. When VCC drops below 2.0 V, it retains stored data as long as a 2 V battery remains connected and all CE pins are held high (ISB3 mode). It does not rewrite data to flash or EEPROM; retention ceases if voltage falls below 2.0 V or if CE is deasserted during backup. This behavior is verified per DSC-2691/17 Table 06 and applies only to LA versions.

How are the interrupt flags INTL and INTR triggered and cleared on 71421LA20JG?

INTL is asserted when the right port writes to address 7FEH (with CER = R/WR = VIL); INTR is asserted when the left port writes to 7FFH. Both flags are cleared by reading the same address with OE enabled (e.g., CEL = OEL = VIL for INTL). The 71421LA20JG does not auto-clear interrupts - software must explicitly access the mailbox. Timing is guaranteed: tINS ≤ 20 ns and tINR ≤ 20 ns for the 20 ns speed grade.

Can 71421LA20JG operate as a standalone dual-port RAM without a MASTER device?

Yes - 71421LA20JG can operate standalone: both ports function asynchronously with independent CE/OE/R/W controls, and BUSY pins default to inactive (high-impedance or pulled up) when unused. However, BUSY-based write arbitration and automatic contention detection require connection to a MASTER's BUSY output. In standalone mode, software must manage concurrent access to avoid data corruption.

What package and pin-compatible alternatives exist for 71421LA20JG in 64-pin TQFP?

The 71421LA20JG is uniquely assigned to the PNG64 (64-pin TQFP) package per IDT documentation. No pin-compatible drop-in replacements exist from IDT or Renesas. Alternative dual-port SRAMs like Cypress CY7C024AV-20AXC use different pinouts, lack BUSY/INT integration, and require redesign of control logic and PCB layout. Migration would necessitate full signal re-mapping and timing validation.