Renesas 70261S35PFI

Overview

70261S35PFI from IDT is a high-speed 16K × 16 true dual-port static RAM with interrupt and semaphore logic, operating at 35 ns max access time, 5 V ±10% supply, and industrial temperature range (−40°C to +85°C), used in real-time inter-processor communication systems requiring concurrent read/write access to shared memory.

For engineers reviewing the 70261S35PFI datasheet, 70261S35PFI pinout, 70261S35PFI application, or 70261S35PFI equivalent, key selection considerations include BUSY arbitration timing (tBDD ≤ 35 ns), interrupt flag behavior (INTL/INTR set/clear via dedicated addresses 3FFE/3FFF), dual-port power-down control (CE-driven standby current ≤ 20 mA), and 100-pin TQFP package compatibility with multiplexed bus systems.

Technical Context

The 70261S35PFI implements fully asynchronous dual-port operation with independent left/right address, control, and I/O buses, enabling simultaneous access to any memory location without external arbitration logic. Its on-chip arbitration supports both address-match and chip-enable–based BUSY assertion, with tAPS = 5 ns priority setup time ensuring deterministic port resolution.

It integrates full hardware semaphore signaling across eight flags (addressed by A0–A2), accessible only when CE = VIH and SEM = VIL, and provides interrupt generation via dedicated mailbox addresses (3FFE for INTL, 3FFF for INTR), where writes trigger flags and reads reset them - all implemented without software overhead.

Key Specifications

Pinout & Package

70261S35PFI is housed in a 100-pin TQFP (PNG100) with 0.5 mm pitch, 14 mm × 14 mm footprint, and 1.4 mm height. All VCC and GND pins must be connected per layout guidelines; no internal voltage regulation is provided.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CY7C1362BV33 and IDT70V261S35PF, the 70261S35PFI uniquely delivers industrial-grade reliability, hardware interrupt/mailbox support, and seamless MASTER/SLAVE cascading - reducing BOM count and firmware complexity in real-time embedded systems.

Availability

70261S35PFI is available at Aetrix Electronics and suitable for real-time inter-processor communication, industrial motion control, and telecom line card buffering requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 70261S35PFI 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, and RF solutions, now part of Renesas Electronics since 2019.

The IDT70261 family was designed for deterministic, low-latency shared-memory architectures in embedded control and communications systems - prioritizing hardware arbitration, interrupt signaling, and seamless port expansion over density or cost.

FAQ

What is the maximum operating frequency supported by the 70261S35PFI?

The 70261S35PFI does not specify a clock frequency; it is an asynchronous SRAM. Its performance is defined by timing parameters: tRC = 35 ns (max read cycle time), meaning it supports effective throughput up to ~28.6 MHz in continuous read cycles. Actual system speed depends on address/control setup/hold times and bus protocol overhead - not a fixed clock domain.

How does the BUSY arbitration work when both ports access the same address simultaneously on the 70261S35PFI?

When both ports assert valid addresses matching within the same cycle, the 70261S35PFI uses tAPS = 5 ns priority setup time to determine which port wins. The winning port proceeds; the losing port's BUSY signal (BUSYL or BUSYR) goes active low (if configured as slave) or high (if master), stalling its write until BUSY deasserts. No data corruption occurs - only controlled delay.

Can the 70261S35PFI be used in a 32-bit data path, and how is that implemented?

Yes - the 70261S35PFI supports 32-bit expansion via MASTER/SLAVE cascading. One device is configured as MASTER (M/S = H), others as SLAVE (M/S = L). The MASTER's BUSY output connects to SLAVE's BUSY input, enabling synchronized arbitration across devices. Separate UBL/LBL and UBR/LBR allow byte-aligned writes across the combined 32-bit bus.

What are the exact memory addresses used for interrupt generation in the 70261S35PFI?

The 70261S35PFI uses fixed SRAM addresses for hardware interrupts: writing to address 3FFF (hex) on the left port asserts the right-port interrupt flag (INTR), and writing to address 3FFE (hex) on the right port asserts the left-port interrupt flag (INTL). Reading those same addresses clears the respective flags - no additional control registers are involved.

Does the 70261S35PFI support partial writes using byte enables, and how is that controlled?

Yes - the 70261S35PFI supports independent upper- and lower-byte writes via UBL/LBL (left port) and UBR/LBR (right port). When UBL = L and LBL = H, only I/O8–I/O15 (upper byte) are written; when UBL = H and LBL = L, only I/O0–I/O7 (lower byte) are written. Both high disables writes; both low enables full 16-bit write - all controlled purely by pin levels, no internal registers.