16Kbit asynchronous SRAM in a 24-DIP — what you're getting
The Cypress CY7C128A-15PC is a 16Kbit (organized as 2K x 8) asynchronous SRAM in a through-hole 24-pin DIP package (0.300" body width, 7.62mm pitch). The parallel interface is straightforward: provide an address, assert chip select and output enable, and data appears on the bidirectional I/O lines within 15 ns. This part is volatile memory, so contents are lost when power drops below the retention threshold.
For a 20 MHz bus with a 50 ns cycle, that leaves 35 ns of margin after the address settles — plenty of timing slack without needing a wait state. If you're replacing a slower SRAM (25 ns or 35 ns) on a legacy board, verify the address-to-data setup timing at the controller; the faster edge may require a small series resistor on the data lines to damp reflections on longer traces.
It belongs in office equipment, indoor telecom line cards, benchtop instruments, or appliance control boards where the ambient stays within a conditioned space. Do not use this in a motor drive enclosure, an outdoor base station, or an engine bay — the silicon will not hold timing or data integrity above 70°C.
Obsolete — how to source it today
Cypress officially marked the CY7C128A-15PC as Obsolete. The only channel for this part is the independent distribution and broker market — new-old-stock (NOS) from surplus inventories, verified date-code lots, and customer-returned tested units. When sourcing, request date-code and test documentation; the longer the gap since the last production run (typically mid-2000s for this generation), the higher the counterfeit risk.
Package and mounting — through-hole for legacy rework
The 24-DIP (0.300", 7.62mm) package is through-hole only — socketed or soldered directly into a PCB. The 0.300" width is the narrow DIP variant, not the wider 0.600" version, so confirm your board's footprint before ordering. If you are reworking a board that originally used a surface-mount SOJ or TSOP SRAM, this DIP will not fit without an adapter.