Infineon Technologies CY7C421-20JXCT

Overview

CY7C421-20JXCT from Cypress Semiconductor is a 512 × 9 asynchronous FIFO memory IC with dual-port RAM architecture, 20 ns access time, 50 MHz max read/write clock rate, TTL-compatible I/O, and standalone/expandable operation supporting width or depth cascading. It serves as a data buffering interface between mismatched-speed digital subsystems in communication controllers and protocol bridges.

For engineers reviewing the CY7C421-20JXCT datasheet, CY7C421-20JXCT pinout, CY7C421-20JXCT application, or CY7C421-20JXCT equivalent, key selection criteria include asynchronous read/write independence, half-full flag timing behavior, retransmit functionality, expansion signaling (XI/XO), and compatibility with legacy 300-mil SOJ and TQFP-32 footprints.

Technical Context

The CY7C421-20JXCT implements a true dual-port RAM core with independent read and write address pointers, enabling fully asynchronous operation without shared clock domains. Its flag logic generates EF (Empty), FF (Full), and HF (Half Full) outputs with deterministic propagation delays relative to control edges.

Expansion support includes XI (Expansion In) and XO/HF (Expansion Out / Half Full) pins that enable depth or width stacking without serial delay accumulation. Retransmit (RT) enables data replay under external control while maintaining R/W enable synchronization and high-impedance output management during idle cycles.

Key Specifications

Pinout & Package

Package: 32-pin TQFP (7 mm × 7 mm, 0.5 mm pitch), RoHS-compliant, surface-mount.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IDT7201L20SOI and AM7201-20JC, CY7C421-20JXCT uniquely provides integrated retransmit control and active Pb-free packaging, making it preferable for new designs requiring data replay functionality and extended lifecycle assurance.

Availability

CY7C421-20JXCT is available at Aetrix Electronics and suitable for industrial protocol bridges, legacy bus interfacing, telecom line card buffering, and test equipment data capture requiring stable component supply and long-term obsolescence mitigation.

Supply support for CY7C421-20JXCT 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 solutions, memory, and interface ICs for industrial, automotive, and communications markets.

The CY7C421 belongs to Cypress's legacy asynchronous FIFO product line, designed specifically for deterministic, low-latency data buffering between asynchronous digital subsystems in mission-critical infrastructure equipment.

FAQ

What is the function of the FL pin on CY7C421-20JXCT?

The FL (First Load) pin configures expansion topology: in width expansion, it connects to VCC; in depth expansion, it grounds the first device in the chain to designate load priority, while all others tie FL to VCC. This ensures correct initialization sequence during cascaded operation and prevents race conditions in multi-device FIFO stacks.

Does CY7C421-20JXCT support simultaneous read and write operations?

Yes - CY7C421-20JXCT supports fully independent asynchronous read and write operations at up to 50 MHz each, with no requirement for synchronized clocks. The dual-port RAM architecture maintains separate read and write address pointers, enabling concurrent access without arbitration or conflict.

How does the HF pin behave in depth expansion mode?

In depth expansion mode, the HF pin functions as Expansion Out (XO), transmitting activation signals to the next device in the cascade. It does not indicate half-full status in this configuration. The datasheet specifies that HF/XO transitions occur with ≤20 ns delay relative to internal clock edges, ensuring tight timing control across stacked devices.

Is CY7C421-20JXCT compatible with 3.3 V logic interfaces?

No - CY7C421-20JXCT is strictly a 5 V TTL-compatible device with VIH minimum of 2.0 V (commercial) and VOL maximum of 0.4 V. Direct connection to 3.3 V logic requires level translation; its inputs are not 5 V-tolerant when powered from 3.3 V, and outputs exceed 3.3 V logic-high thresholds.