Memory density and bus timing for legacy 5V parallel designs
The CY7C199CN-15ZXCT is a 256Kbit asynchronous SRAM organized as 32K x 8 bits, with a 15 ns access time that sets the ceiling for read-cycle timing on a parallel bus. The 15 ns access time means the memory can complete a read within 15 ns of the address being valid. For a system with a 33 MHz bus clock (30 ns period), this leaves 15 ns of margin after the address settles before the data must be latched — adequate for most asynchronous bus controllers, but tight if the controller adds its own propagation delay.
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Package and board-fit for the 28-TSSOP footprint
The supplier device package is designated 28-TSOP I — the two terms refer to the same mechanical outline. Tape & Reel packaging supports pick-and-place reflow soldering.