Renesas 71321SA35TFG

Overview

71321SA35TFG from IDT (now Renesas) is a high-speed 2K × 8 dual-port static RAM with interrupt and BUSY arbitration logic, designed as a MASTER device for interprocessor communication. It delivers 35 ns max read cycle time, supports fully asynchronous dual-port access, operates on single 5V ±10% supply, and features open-drain BUSY/INT outputs requiring 270 Ω pull-up resistors - used in real-time embedded control systems where deterministic port contention resolution is required.

For engineers reviewing the 71321SA35TFG datasheet, 71321SA35TFG pinout, 71321SA35TFG application, or 71321SA35TFG equivalent, key selection criteria include its MASTER-only arbitration logic, 35 ns speed grade, TQFP-64 package, industrial temperature support (–40°C to +85°C), and compatibility with IDT71421SLAVE devices for 16-bit+ memory expansion.

Technical Context

The 71321SA35TFG implements hardware-based port arbitration using address- and CE-driven BUSY assertion, with tBAA/tBAC ≤ 30 ns timing for BUSY generation. Its interrupt logic uses dedicated mailbox addresses (7FE_H for INTL, 7FF_H for INTR) triggered by cross-port writes, with tINS/tINR ≤ 45 ns interrupt set/reset timing.

It supports two independent asynchronous ports (left/right), each with separate A0–A10, I/O0–I/O7, R/W, CE, OE, and interrupt/BUSY signals. The device includes on-chip power-down control via CE, enabling ISB1 ≤ 25 mA (both ports TTL standby) and ISB3 ≤ 1.0 mA (full CMOS standby) at 5V.

Key Specifications

Pinout & Package

71321SA35TFG is packaged in a 64-pin TQFP (PNG64) with 0.5 mm pitch, body size 14 mm × 14 mm × 1.4 mm. All VCC pins must be decoupled locally; all GND pins require low-inductance ground plane connection.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 71321SA25TFG and 71321LA35TFG, the 71321SA35TFG offers optimal balance of speed and industrial standby power - delivering 35 ns performance without battery-retention circuitry, making it ideal for mains-powered real-time systems needing deterministic arbitration.

Availability

71321SA35TFG is available at Aetrix Electronics and suitable for real-time motor control, multi-core communication buffers, and redundant PLC I/O modules requiring stable component supply across extended production lifecycles.

Supply support for 71321SA35TFG 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

IDT (Integrated Device Technology), now part of Renesas Electronics, is a fabless semiconductor company specializing in high-performance memory, timing, and interface solutions for communications and industrial markets.

The 71321SA35TFG belongs to IDT's dual-port SRAM product line, engineered specifically for deterministic interprocessor communication in hard real-time embedded systems where software-managed shared memory introduces unacceptable latency or jitter.

FAQ

What is the function of the BUSY pins on the 71321SA35TFG?

The BUSYL and BUSYR pins on the 71321SA35TFG are open-drain outputs that signal port contention when both ports attempt simultaneous access to the same memory location. As a MASTER device, the 71321SA35TFG asserts BUSY to inhibit writes on the contending port - ensuring data integrity without external arbitration logic. Each BUSY pin requires a 270 Ω pull-up resistor to VCC per datasheet Figure 3.

Can the 71321SA35TFG operate as a SLAVE device in a MASTER/SLAVE configuration?

No, the 71321SA35TFG is exclusively a MASTER device. Its BUSY pins are outputs, and it contains on-chip arbitration logic - functionality reserved for MASTER operation per datasheet Functional Description and Truth Table III. To build a width-expanded array, pair the 71321SA35TFG with IDT71421SLAVE devices, whose BUSY pins are inputs and lack arbitration logic.

How do the interrupt flags (INTL and INTR) work on the 71321SA35TFG?

INTL is asserted when the right port writes to address 7FE_H; INTR is asserted when the left port writes to 7FF_H. Both flags are open-drain and require pull-up resistors. Clearing is performed by reading the respective address (7FE_H clears INTL; 7FF_H clears INTR) with CE and OE active. This mailbox mechanism enables zero-overhead interprocessor signaling without polling - a core capability of the 71321SA35TFG.

What is the maximum operating temperature range supported by the 71321SA35TFG?

The 71321SA35TFG is rated for industrial temperature operation from –40°C to +85°C, as confirmed in the "Recommended Operating Temperature and Supply Voltage" table (2691 tbl 02). This rating applies to the 35 ns speed grade and is validated across all electrical parameters including tRC = 35 ns, ISB1 ≤ 25 mA, and BUSY timing (tBAA ≤ 30 ns), making it suitable for under-hood automotive ECUs and factory-floor controllers.

Is the 71321SA35TFG pin-compatible with other members of the IDT71321/71421 family?

Yes - the 71321SA35TFG shares identical pinout and footprint with all 64-pin TQFP variants in the IDT71321/71421 family, including 71321SA20TFG, 71321SA25TFG, and 71321LA35TFG. Signal mapping, power/ground pin locations, and package dimensions (14 mm × 14 mm × 1.4 mm) are fully consistent, enabling drop-in replacement for speed or power optimization without PCB revision.