Renesas 70261S55PF

Overview

70261S55PF from IDT (now Renesas) is a high-speed 16K × 16 true dual-port static RAM with interrupt and semaphore logic, operating at 55 ns max access time, 5 V ±10% supply, and industrial temperature range (–40°C to +85°C). It enables simultaneous asynchronous read/write access from independent left/right ports in real-time communication buffers and multiprocessing interconnects.

For engineers reviewing the 70261S55PF datasheet, 70261S55PF pinout, 70261S55PF application, or 70261S55PF equivalent, key selection criteria include dual-port arbitration timing (tBDD ≤ 40 ns), interrupt flag latency (tINS ≤ 40 ns), semaphore contention window (tSPS = 5 ns), and 100-pin TQFP mechanical compatibility for legacy board reuse.

Technical Context

The 70261S55PF implements fully asynchronous dual-port architecture with separate address, control, and I/O buses per port, enabling concurrent memory access without external arbitration logic. Its on-chip hardware supports BUSY flag generation via address-match arbitration and interrupt signaling via dedicated mailbox addresses (3FFE_H, 3FFF_H).

It integrates full semaphore logic with eight user-accessible flags addressed by A0–A2, controlled via SEM/CE polarity inversion (CE = VIH & SEM = VIL for semaphore access). Power management uses TTL-compatible CE-driven automatic power-down, achieving ISB3 ≤ 5 µA (full standby, CMOS inputs) and ICC ≤ 150 mA (both ports active, fMAX).

Key Specifications

Pinout & Package

70261S55PF is housed in a 100-pin Thin Quad Flatpack (TQFP) with 0.5 mm pitch, body size 14 mm × 14 mm × 1.4 mm. All VCC and GND pins must be connected per layout guidelines; N/C pins are internally unconnected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY7C1362BV33-55AXI and IDT70V261S15PF, the 70261S55PF uniquely combines industrial temperature rating, hardware semaphore logic, and interrupt mailbox functionality in a single 5 V, 100-pin TQFP package-enabling drop-in replacement in legacy multiprocessing systems without redesign.

Availability

70261S55PF is available at Aetrix Electronics and suitable for real-time multiprocessor communication, industrial PLC memory buffering, and telecom line card interconnect requiring stable component supply across extended product lifecycles.

Supply support for 70261S55PF 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

Renesas Electronics (formerly Integrated Device Technology) is a global semiconductor leader specializing in microcontrollers, analog, power management, and memory solutions for industrial, automotive, and communications markets.

The IDT70261 family was designed specifically for high-reliability multiprocessing systems requiring deterministic, hardware-accelerated inter-processor communication via dual-port SRAM with integrated arbitration and signaling logic.

FAQ

What is the maximum access time specification for the 70261S55PF?

The 70261S55PF has a maximum access time of 55 ns, measured as tAA (address access time) and tACE (chip enable access time) under industrial temperature conditions (–40°C to +85°C) and 5 V ±10% supply. This value defines the guaranteed worst-case delay from valid address/enable assertion to stable data output, critical for timing closure in high-speed synchronous interfaces.

Does the 70261S55PF support true simultaneous access to the same memory location from both ports?

Yes, the 70261S55PF implements true dual-port SRAM cells that allow simultaneous read/write access to identical addresses. When contention occurs, on-chip arbitration asserts BUSY on the later-arriving port, allowing the first access to complete. This behavior is confirmed in Truth Table IV and Timing Waveform 12, ensuring deterministic operation without external logic.

How does the interrupt function work in the 70261S55PF?

The 70261S55PF uses dedicated mailbox addresses: writing to 3FFF_H on the left port asserts INTR (right port interrupt), and writing to 3FFE_H on the right port asserts INTL (left port interrupt). Clearing is performed by reading the same address. Timing is specified in Table 15b (tINS ≤ 40 ns), and operation is detailed in Functional Description page 15 and Truth Table III.

What is the role of the M/S pin on the 70261S55PF?

The M/S (Master/Slave) pin configures the 70261S55PF for cascaded operation: M/S = H makes BUSYL/BUSYR outputs (master mode), while M/S = L makes them inputs (slave mode). This enables 32-bit or wider memory expansion using multiple devices, where one master coordinates BUSY arbitration across slaves-eliminating need for discrete logic in wide-data systems.

Can the 70261S55PF operate in low-power standby modes, and what are the current values?

Yes, the 70261S55PF supports four standby modes. Full standby (ISB3) draws ≤ 5 µA when both ports are disabled with CMOS-level inputs. One-port standby (ISB4) draws ≤ 135 mA (typical) when one port is active. These values are specified in Table 10 for industrial grade and enable energy-efficient operation in battery-backed or thermally constrained systems.