Infineon Technologies CY7C421-15AXCT

Overview

CY7C421-15AXCT from Cypress Semiconductor is a 512 × 9 asynchronous FIFO memory IC with dual-port RAM architecture, 50 MHz max read/write throughput, 15 ns access time, and TTL-compatible I/O. It provides independent read/write clocks, empty/full/half-full flags, retransmit capability, and supports width/depth expansion in industrial-grade (–40°C to +85°C) operation at 5 V ±10%.

For engineers reviewing the CY7C421-15AXCT datasheet, CY7C421-15AXCT pinout, CY7C421-15AXCT application, or CY7C421-15AXCT equivalent, key selection factors include asynchronous depth expansion timing, HF flag behavior in standalone vs. cascaded mode, retransmit control sequence, and compatibility with IDT7201/AM7201 in pin- and function-matched systems.

Technical Context

The CY7C421-15AXCT implements a true dual-port asynchronous FIFO using 0.65-μm P-well CMOS, with independent write (W) and read (R) strobes controlling separate address pointers. Its expansion logic enables depth chaining via XI/XO signals without serial propagation delay penalty.

Flag generation is synchronous to respective control edges: EF goes LOW on read of last valid word; FF goes LOW after write to full buffer; HF asserts LOW when 256 words are stored. In depth expansion, XO replaces HF and signals activation to downstream FIFOs.

Key Specifications

Pinout & Package

Package: 32-pin PLCC (7 × 7 mm), RoHS-compliant, lead-free.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar asynchronous FIFO applications.

Compared with IDT7201LA15TPG and AM7201-15JC, CY7C421-15AXCT uniquely integrates retransmit and half-full flag in an industrial-grade package, eliminating external glue logic while ensuring robustness across automotive and industrial thermal profiles.

Availability

CY7C421-15AXCT is available at Aetrix Electronics and suitable for telecom line card buffering, industrial PLC data acquisition, and automotive infotainment gateway designs requiring stable component supply and long-term lifecycle support.

Supply support for CY7C421-15AXCT 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

Cypress Semiconductor (now part of Infineon Technologies) is a U.S.-based semiconductor company specializing in programmable system-on-chip, memory, and interface solutions for embedded and industrial markets.

CY7C421 belongs to Cypress's legacy FIFO memory product line, designed specifically for high-reliability, asynchronous data buffering between dissimilar clock domains in telecom, industrial control, and defense systems.

FAQ

What is the function of the FL pin in depth expansion mode?

The FL (First Load) pin determines device ordering in a depth-expanded FIFO chain: grounding FL on the first device signals it to accept initial writes, while all downstream devices have FL tied to VCC to defer loading until upstream FIFOs are full. This ensures deterministic fill sequencing without external arbitration logic.

How does the XO/HF pin behave differently in standalone versus depth expansion configurations?

In standalone or width expansion, XO/HF functions as a half-full flag (LOW when 256 words stored). In depth expansion, it becomes an expansion-out signal that goes LOW to activate the next FIFO in the chain upon reaching capacity. The mode is determined by circuit configuration-not internal register setting.

Can the CY7C421-15AXCT operate with mixed voltage interfaces?

No. The CY7C421-15AXCT is strictly 5 V TTL-compatible with VIH(min) = 2.0 V (commercial) or 2.2 V (industrial), and VOL(max) = 0.4 V. It lacks internal level-shifting and must be interfaced only with 5 V logic families; direct connection to 3.3 V or 1.8 V systems requires external translators.

What timing constraint governs safe retransmit operation?

Retransmit requires simultaneous HIGH on MR and R, with W also HIGH; then R toggling LOW retrieves the last-read word. Violating this sequence-such as asserting RT without MR HIGH-results in undefined pointer behavior. The tRTC (25 ns) minimum retransmit cycle time must be observed between successive R pulses during retransmit mode.