Renesas 71321SA20J8

Overview

71321SA20J8 from Integrated Device Technology (IDT) is a high-speed 2K × 8 dual-port static RAM with on-chip interrupt logic and port arbitration, designed as a MASTER device for interprocessor communication systems. It supports 20 ns max read cycle time, operates at 5V ±10%, delivers 325 mW typical active power, and features open-drain BUSY/INT outputs requiring 270 Ω pull-up resistors. It is used in real-time embedded control subsystems where concurrent CPU and DSP access to shared memory is required.

For engineers reviewing the 71321SA20J8 datasheet, 71321SA20J8 pinout, 71321SA20J8 application, or 71321SA20J8 equivalent, this page provides verified technical context, exact pin-level design meaning, confirmed timing parameters for interrupt and BUSY arbitration, and validated alternative parts for master-side dual-port SRAM replacement in industrial control and telecom baseband designs.

Technical Context

The 71321SA20J8 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 generation based solely on chip enable (CEL/CER) and address match - not R/W state - enabling deterministic write inhibition during simultaneous access to identical addresses.

As a MASTER device, it drives BUSYL and BUSYR as open-drain outputs (requiring external 270 Ω pull-ups), while supporting two independent interrupt flags (INTL and INTR) tied to dedicated mailbox addresses (7FEh and 7FFh). Interrupt assertion occurs on write to those locations; clearing requires read or write with OE/CE asserted - no internal auto-clear logic.

Key Specifications

Pinout & Package

71321SA20J8 is packaged in a 52-pin STQFP (PPG52), measuring 10 mm × 10 mm × 1.4 mm, with exposed pad for thermal dissipation. All VCC pins must be decoupled locally; all GND pins require low-impedance ground plane connection.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY7C1362BV25 and IDT71421SA20J8, the 71321SA20J8 uniquely integrates MASTER arbitration and dual interrupt flags in a single 5V device - eliminating external logic, reducing BOM count by ≥3 components, and guaranteeing deterministic 20 ns interrupt response without software intervention.

Availability

71321SA20J8 is available at Aetrix Electronics and suitable for industrial PLC backplanes, telecom baseband modules, avionics data concentrators, and medical imaging subsystems requiring stable component supply, long-term lifecycle assurance, and guaranteed traceable sourcing.

Supply support for 71321SA20J8 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 sensor signal conditioning ICs for communications, computing, and industrial markets.

The IDT71321 product line was engineered specifically for deterministic, low-latency interprocessor communication in real-time embedded systems - emphasizing hardware arbitration, interrupt offload, and 5V robustness for legacy and mixed-voltage environments.

FAQ

What is the function of the BUSY pins on the 71321SA20J8?

The BUSYL and BUSYR pins on the 71321SA20J8 are open-drain outputs that assert LOW when the opposite port initiates an access to the same memory address. This signal blocks writes on the contending port, preventing data corruption. Each BUSY pin requires a 270 Ω external pull-up resistor to VCC to establish a valid HIGH level. The 71321SA20J8 implements this logic internally - no external arbitration circuitry is needed.

Can the 71321SA20J8 operate with only one port enabled?

Yes, the 71321SA20J8 supports independent port operation. When CEL = VIH, the left port enters standby mode (ISB1 = 30 mA typ.); when CER = VIH, the right port does likewise. Either port can remain fully active while the other is disabled - enabling asymmetric usage such as FPGA-to-CPU communication where only one side initiates transfers. The 71321SA20J8 retains full functionality including interrupt generation even with one port inactive.

How do the INTL and INTR interrupts work on the 71321SA20J8?

INTL asserts when the right port writes to address 7FEh; INTR asserts when the left port writes to 7FFh. Both flags are open-drain and require pull-up resistors. To clear INTL, the left port must access 7FEh with CEL = OEL = VIL; to clear INTR, the right port accesses 7FFh similarly. These are hardware mailbox registers - the 8-bit data written is user-defined and retained in SRAM. The 71321SA20J8 provides no auto-clear or edge-triggered behavior - timing is governed by tINS (20 ns max).

Is the 71321SA20J8 pin-compatible with the IDT71421SA20J8?

No, the 71321SA20J8 and IDT71421SA20J8 are not pin-compatible. While both use the same 52-pin STQFP package, their BUSY pins have opposite roles: on the 71321SA20J8, BUSYL/BUSYR are outputs; on the IDT71421SA20J8, they are inputs. Swapping them causes functional failure - the 71321SA20J8 would drive conflicting signals onto SLAVE BUSY lines. The 71321SA20J8 is MASTER-only; IDT71421SA20J8 is SLAVE-only.

Does the 71321SA20J8 support battery backup or low-voltage retention?

No, the 71321SA20J8 (SA suffix) does not support battery backup or data retention below 4.5 V. Only the LA-suffix variants (e.g., 71321LA20J8) provide 2 V data retention capability with ISB3 = 0.2 mA typ. The SA version is optimized for performance and commercial/industrial temperature operation (–40°C to +85°C) at full 5V supply - its standby current drops to 30 mA typ. but ceases memory retention below VCC min.