Infineon (formerly Cypress Semiconductor) lists the CY7C199CN-12ZXCT as obsolete.
12 ns access time — the timing decision
The headline 12 ns access time sets the bus timing budget for this 256Kbit asynchronous SRAM. In a system with a 5V bus, that 12 ns window determines how fast the memory controller can assert chip select and address before data appears on the I/O lines. For a 33 MHz or slower bus, this part leaves comfortable margin; at higher clock rates the 12 ns figure starts to consume a significant fraction of the cycle, so verify hold and setup against your controller's timing parameters.
32K x 8 organization and 5V-only supply
Organized as 32K words by 8 bits, this SRAM presents a byte-wide parallel interface — straightforward to hook to an 8-bit microcontroller or as a data buffer in a legacy DSP system.
Package and footprint — 28-TSOP I
Housed in a 28-TSOP I package (0.465" body width, 11.80 mm), this is a surface-mount device. The Tape & Reel suffix (ZXCT) means it ships on a reel for automated pick-and-place.