Renesas 70261S35PFI8

Overview

70261S35PFI8 from IDT is a high-speed 16K × 16 true dual-port static RAM with interrupt and semaphore logic, operating at 35 ns access time (max), supporting independent asynchronous read/write on left and right ports, and designed for real-time inter-processor communication in embedded control systems.

For engineers reviewing the 70261S35PFI8 datasheet, 70261S35PFI8 pinout, 70261S35PFI8 application, or 70261S35PFI8 equivalent, key selection considerations include its 100-pin TQFP package, industrial temperature range (–40°C to +85°C), 5 V ±10% supply, BUSY/INT arbitration support, and dual-port contention resolution via hardware semaphore flags.

Technical Context

The 70261S35PFI8 implements fully asynchronous dual-port operation with separate address, control, and I/O buses per port - enabling simultaneous access to any memory location without external arbitration logic. Its on-chip arbitration uses push-pull BUSY outputs (not open-drain) and supports both address-match and chip-enable controlled BUSY assertion modes.

It integrates dedicated interrupt flag registers at addresses 3FFE_H (left port INTL) and 3FFF_H (right port INTR), plus eight hardware semaphores addressed by A0–A2 and accessed via SEM = VIL, CE = VIH. Semaphore writes use I/O0 only; reads return data across all 16 I/O lines.

Key Specifications

Pinout & Package

70261S35PFI8 is housed in a 100-pin Thin Quad Flatpack (TQFP) with exposed pad not electrically connected. All 100 pins are assigned; no NC pins are used for signal routing. Pin 1 is located at top-left corner (marked dot), with numbering counterclockwise.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY7C1362BV33-166BZXI and IDT70V261S25PFGI, the 70261S35PFI8 offers guaranteed 5 V TTL compatibility, fully asynchronous operation, and industrial temperature support without requiring clock distribution or voltage translation - making it optimal for retrofitting legacy 5 V control systems.

Availability

70261S35PFI8 is available at Aetrix Electronics and suitable for industrial PLC backplanes, avionics data concentrators, telecom line cards, motor drive controllers, and real-time inter-processor communication systems requiring stable component supply across extended product lifecycles.

Supply support for 70261S35PFI8 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) is a fabless semiconductor company specializing in timing, memory interface, RF, and high-performance silicon solutions, now part of Renesas Electronics since 2019.

The IDT70261 family was engineered for deterministic, low-latency inter-processor communication in mission-critical embedded systems - emphasizing hardware arbitration, interrupt signaling, and seamless 5 V integration without external glue logic.

FAQ

What is the maximum access time specification for the 70261S35PFI8?

The 70261S35PFI8 has a maximum access time of 35 ns (tAA, tACE, tABE) over the full industrial temperature range (–40°C to +85°C) and 5.0 V ±10% supply. This value is production-tested and guaranteed - not characterized only - and applies to both left and right ports under worst-case voltage and temperature conditions.

Does the 70261S35PFI8 support true simultaneous read/write to the same memory address?

Yes, the 70261S35PFI8 implements true dual-port memory cells that permit simultaneous access to the same location. However, when both ports attempt write operations to identical addresses, on-chip arbitration asserts BUSY on the later-arriving port to prevent corruption - the 70261S35PFI8 ensures deterministic resolution, not concurrent writes.

How is semaphore functionality implemented in the 70261S35PFI8?

The 70261S35PFI8 provides eight hardware semaphore flags accessed by setting SEM = VIL and CE = VIH, then using A0–A2 to select the flag. Writing to I/O0 sets the flag; reading returns the value across all 16 I/O lines. The 70261S35PFI8 handles arbitration internally - no software polling or external logic is needed to manage mutual exclusion.

Can the 70261S35PFI8 be used in a MASTER/SLAVE configuration for 32-bit data paths?

Yes, the 70261S35PFI8 supports MASTER/SLAVE cascading via the M/S pin: set M/S = H on one device (BUSY output) and M/S = L on the other (BUSY input). This configuration enables error-free 32-bit word expansion without additional discrete logic - the 70261S35PFI8's on-chip arbitration ensures synchronized operation between cascaded units.

What are the interrupt mailbox addresses for the 70261S35PFI8?

The 70261S35PFI8 uses fixed SRAM addresses for interrupt signaling: writing to address 3FFE_H (hex) asserts the left port's INTL flag, and writing to 3FFF_H asserts the right port's INTR flag. Clearing is performed by reading those same addresses - the 70261S35PFI8 treats these as standard memory locations, allowing user-defined 16-bit messages to be passed alongside the interrupt event.