Functional Description
The CY7C421 is a first-in first-out (FIFO) memory offered in 300-mil wide SOJ, TQFP & PLCC packages and it is 512 words by 9 bits wide. Each FIFO memory is organized such that the data is read in the same sequential order that it was written. Full and empty flags are provided to prevent overflow and underflow. Three additional pins are also provided to facilitate unlimited expansion in width, depth, or both. The depth expansion technique steers the control signals from one device to another in parallel. This eliminates the serial addition of propagation delays, so that throughput is not reduced. Data is steered in a similar manner.

FEATUREs
■ Asynchronous First-In First-Out (FIFO) Buffer Memories
   ❐ 512 × 9 (CY7C421)
■ Dual-Ported RAM Cell
■ High Speed 50 MHz Read and Write Independent of Depth and Width
■ Low Operating Power: ICC = 35 mA
■ Empty and Full Flags (Half Full Flag in Standalone)
■ TTL Compatible
■ Retransmit in Standalone
■ Expandable in Width
■ PLCC, 7 × 7 TQFP, 300-Mil Molded SOJ
■ Pb-free Packages Available
■ Pin Compatible and Functionally Equivalent to IDT7201, and AM7201