Infineon Technologies CY7C421-15AXC

Overview

CY7C421-15AXC from Cypress Semiconductor is a 512 × 9 asynchronous FIFO memory IC with dual-ported RAM architecture, 50 MHz max read/write throughput, 15 ns access time, and TTL-compatible I/O. It provides independent full (FF), empty (EF), and half-full (HF) flags and supports width/depth expansion for system-level buffering in serial data bridges and protocol translators.

For engineers reviewing the CY7C421-15AXC datasheet, CY7C421-15AXC pinout, CY7C421-15AXC application, or CY7C421-15AXC equivalent, key selection criteria include asynchronous depth expansion capability, retransmit (RT) function for packet replay, HF flag behavior in standalone mode, and compatibility with IDT7201/AM7201 in pinout and timing.

Technical Context

The CY7C421-15AXC implements a true asynchronous FIFO using dual-port RAM with independent write (W) and read (R) control paths, enabling concurrent 50 MHz operation regardless of fill level. Its expansion logic supports unlimited width/depth cascading via XI/XO pins without serial propagation delay penalty.

Flag generation is synchronous to respective control edges: EF asserts on read underflow, FF on write overflow, and HF transitions at exactly 256-word occupancy. Retransmit mode requires both R and W high before initiating sequential readout from the first valid word.

Key Specifications

Pinout & Package

Package: 32-pin PLCC (7 × 7 mm TQFP also supported per datasheet). Pinout validated from Cypress Document No. 38-06001 Rev. *K, Page 4–5.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT7201LA15TPG and AM7201-15JC, the CY7C421-15AXC uniquely delivers hardware retransmit capability and industrial temperature support in a single package-critical for deterministic replay in diagnostic logging and robust operation in harsh environments.

Availability

CY7C421-15AXC is available at Aetrix Electronics and suitable for industrial serial bridges, legacy protocol translators, test equipment data capture, and embedded diagnostic loggers requiring stable component supply and long-term obsolescence management.

Supply support for CY7C421-15AXC 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) designs high-reliability memory and programmable logic solutions for industrial, automotive, and communications systems.

The CY7C421 belongs to Cypress's legacy asynchronous FIFO product line, engineered specifically for clock-domain isolation and burst-data buffering in mixed-signal instrumentation and protocol gateway applications.

FAQ

What is the function of the FL pin on CY7C421-15AXC?

The FL (First Load) pin configures expansion topology: in width expansion it connects to VCC; in depth expansion it grounds the first device to indicate load priority, while others tie FL to VCC. This ensures correct initialization sequence across cascaded FIFOs and prevents race conditions during power-up.

Does CY7C421-15AXC support simultaneous read and write operations?

Yes-CY7C421-15AXC supports fully asynchronous read and write operations at up to 50 MHz each, with independent control signals (W and R) and separate internal pointers. The dual-port RAM architecture guarantees no contention or arbitration delay between concurrent accesses.

How does the Half-Full (HF) flag behave in depth expansion mode?

In depth expansion mode, the HF pin functions as Expansion Out (XO) to signal activation of the next FIFO in the chain. It does not reflect half-full status in this configuration-only in standalone or width-expanded setups where XO/HF retains its flag role.

What is the maximum capacitive load the CY7C421-15AXC outputs can drive?

The CY7C421-15AXC is characterized for 30 pF total load capacitance (including scope/jig) per output, as defined in AC Test Loads Figure 4. Driving loads beyond 30 pF may exceed specified tHZR and tDVR timing margins and cause setup/hold violations in downstream receivers.