Asynchronous FIFO with 20 ns access — a legacy workhorse in 32-PLCC
The Cypress CY7C425-20JXC is a 9K (1K x 9) asynchronous FIFO memory with a 20 ns access time and 50 MHz data rate.
In an asynchronous system, this timing must fit within the host controller's setup-and-hold budget. The 50 MHz data rate means the FIFO can sustain a 50 million word/second transfer when both read and write clocks are active, assuming FIFO fullness does not stall either side. The part is uni-directional (data flows one way through the FIFO), which is typical for rate-matching between a fast ADC and a slower bus, or between two clock domains in a telecom line card.
Obsolete — sourcing reality for CY7C425-20JXC
The CY7C425-20JXC is listed as obsolete. No official replacement or second-source alternate is documented.