Renesas 71321SA20PF

Overview

71321SA20PF from Integrated Device Technology is a high-speed 2K × 8 dual-port static RAM with on-chip port arbitration logic, two interrupt flags (INTL/INTR), and open-drain BUSY output - designed as the MASTER device in master/slave memory expansion systems. It delivers 20 ns max read cycle time, operates at 5V ±10%, supports industrial temperature range (–40°C to +85°C), and enables error-free 16-bit-or-wider data bus expansion without external logic.

For engineers reviewing the 71321SA20PF datasheet, 71321SA20PF pinout, 71321SA20PF application, or 71321SA20PF equivalent, this page provides verified technical context, exact pin functions for PLCC-52 package, real-world arbitration timing constraints, and validated alternatives for interprocessor communication designs requiring deterministic port-to-port handshaking.

Technical Context

The 71321SA20PF implements fully asynchronous dual-port operation with independent left/right address, control, and I/O buses. Its on-chip arbitration logic resolves contention via BUSY flag assertion based solely on chip enable (CEL/CER) and address match timing - not R/W state - ensuring deterministic write inhibition when both ports access the same location.

Interrupt functionality uses dedicated mailbox addresses (7FE_H for INTL, 7FF_H for INTR) with set/reset timing defined by tINS ≤ 20 ns and tINR ≤ 20 ns. BUSY outputs are open-drain and require 270 Ω pull-up resistors; BUSYL/BUSYR cannot be low simultaneously, guaranteeing exclusive port access resolution.

Key Specifications

Pinout & Package

71321SA20PF is packaged in 52-pin Plastic Leaded Chip Carrier (PLCC), body size ≈ 19.05 mm × 19.05 mm × 4.32 mm, with gull-wing leads and internal heat slug. Pin 1 marked by corner notch; pins numbered counterclockwise.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY7C133-25JC, 71321SA20PF reduces BOM count and layout risk by integrating arbitration and interrupts; compared with IDT71421SA20PF, it provides autonomous conflict resolution essential for single-dual-port implementations.

Availability

71321SA20PF is available at Aetrix Electronics and suitable for real-time motion control, multi-core communication buffers, industrial PLC I/O mapping, and legacy bus bridge interfaces requiring stable component supply, long-term lifecycle assurance, and industrial-grade reliability.

Supply support for 71321SA20PF 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, RF, and high-performance computing solutions.

The IDT71321 family was engineered specifically for deterministic interprocessor communication in industrial and telecom systems - delivering hardware-enforced memory coherency without software intervention.

FAQ

What is the function of BUSYL on the 71321SA20PF?

BUSYL is an open-drain output flag on the 71321SA20PF that signals port contention when both left and right ports attempt to access the same memory location. It requires a 270 Ω pull-up resistor to VCC and asserts low to inhibit writes on the left port - a core feature enabling deterministic arbitration in master/slave configurations. This behavior is intrinsic to the 71321SA20PF as the MASTER device.

Can the 71321SA20PF operate with a 3.3V supply?

No. The 71321SA20PF is specified exclusively for 5V ±10% operation (4.5 V to 5.5 V). Its input thresholds (VIH ≥ 2.2 V, VIL ≤ 0.8 V) and internal circuitry are designed for TTL-compatible 5V logic levels. Using 3.3V violates the Absolute Maximum Ratings and will result in undefined operation or permanent damage. For 3.3V dual-port SRAMs, consider newer families such as IDT70V27L.

How does interrupt handling work in the 71321SA20PF?

The 71321SA20PF uses dedicated SRAM addresses 7FE_H (for INTL) and 7FF_H (for INTR) as hardware mailboxes. Writing to 7FF_H from the left port asserts INTR low; reading 7FF_H from the right port clears it. Similarly, 7FE_H controls INTL. Timing is guaranteed: tINS ≤ 20 ns and tINR ≤ 20 ns. These flags are open-drain and require external pull-ups - a key design detail for reliable 71321SA20PF interrupt implementation.

Is the 71321SA20PF pin-compatible with the 71421SA20PF?

No. While both use PLCC-52 packaging and share identical pin numbering, their BUSY pin functions differ fundamentally: on the 71321SA20PF, BUSYL/BUSYR are outputs (MASTER), whereas on the 71421SA20PF they are inputs (SLAVE). Swapping them causes functional failure - the 71421SA20PF lacks arbitration logic and cannot generate BUSY signals. They are complementary, not interchangeable.

What is the maximum junction temperature for continuous operation of the 71321SA20PF?

The 71321SA20PF is rated for industrial temperature operation from –40°C to +85°C ambient. Its Absolute Maximum Rating for Temperature Under Bias (TBIAS) is +125°C, but sustained operation above +85°C ambient requires derating based on package thermal resistance (θ_JA ≈ 50°C/W typical for PLCC-52) and actual power dissipation. At 110 mA active current (550 mW), junction temperature rise is ~27.5°C - keeping T_J within safe limits only if board-level cooling maintains ambient ≤ +85°C.